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Reigen Arataka was a notorious lightweight; he knew it, his coworkers knew it and even some of the clients knew it. That was why he kept a strict eye on his beer glass, making sure that it was just full enough that no one would pour him more.

He was out with a group of fellow salesman at a local dive bar. It was the sort of place that reeked of cigarettes, stale beer and desperation. Reigen’s company had just closed on a huge account for a major accounting firm; Big Cool Water company was now the exclusive water cooler distributers for Accountants Inc. “Small victories for small minds,” Reigen thought.

Representatives from the accounting firm were also present at this little celebration, much to Reigen’s chagrin. Especially since he had slept with one of them, especially since said accountant was now making eyes at him and, oh god, Ito-san was coming this way. With dark hair, fashionable glasses and an impeccable suit, Ito was lusted over by many of the ladies at the gathering.

Unfortunately for them and Reigen, he had his eyes set on a skinny blonde salesman with a terrible head for beer.

“Arataka,” Ito purred, clapping an unwelcome hand on Reigen’s shoulder. It sat there with far too much familiarity.

Reigen bristled; one half-decent blowjob did not entitle Ito to—

“You look a little thirsty,” Ito said and before Reigen could say anything, his glass was filled to over-flowing. Reigen was forced to slurp some of it down to prevent the beer from spilling all over him. Ito was such an asshole. “There we go,” the accountant cooed.

Oh great, now Reigen’s head was swimming. Damn it, Ito. “With the deal over, you’ll be going back to Capital City, won’t you?” Reigen asked, hoping that Ito would get the hint. The hint that he should leave; the hint that “Oh sorry, my mother’s arranging a match for me, this is just a one-night thing” Ito-san wasn’t welcome in Reigen’s personal space.

The hand on Reigen’s shoulder tightened. “I think I might stick around for a few more days,” Ito said, lips far too close to Reigen’s ear.

Not if Reigen could help it. One of his coworkers jostled into him and, once again, to prevent a spill, he took a drink. Then another sip, then he figured, fuck it and downed the whole thing. Can’t spill it if it’s empty. Everything went fuzzy and his limbs were heavy and Ito was eyeing him again. Yup, drinking that whole beer was a mistake.

“I’m out,” Reigen said, stumbling to his feet. He only hoped to get out before he embarrassed himself in front of the rest of the sales staff.

“Let me walk you home,” Ito offered.

Nope, Reigen was not that drunk. He knew that civility was not what was on Ito’s mind. “I’m fine,” Reigen said.

“I insist.”

Asshole. Asshole. Asshole.

The two of them staggered out into the dark night, Reigen fending off Ito’s “friendly” offers all the while. “Come on, what’s the big deal?” Ito asked, pawing at him. “We had a good time, why can’t we have another?”

“The big deal is I don’t want to do this,” Reigen said, shoving the accountant away. “I want something real, not just be some salaryman’s booty call.”

“Booty call,” Ito criticized, as if Reigen’s word choice were the issue.

Reigen rolled his eyes and walked away. Ito called out after him but the salesman ignored him. Ito didn’t even live in Seasoning; he was just a temporary issue. Once he was gone Reigen could go back to the serious business of being lonely.

Reigen let his feet just take him wherever, not bother to pay any attention. He was drunk, he was frustrated and he was, well, alone. The first thing that hit him was the smell of the sea. He blinked, focusing for the first time in at least a full half-hour. The dark night shimmered off the surface of the water, bathing it in starlight. It wasn’t as grand as it would be in the country, but Reigen would take it. The pier was deserted at this hour, he could go down to the shore and wander if he wanted, maybe even dip his toes into the cool water.

That sounded nice. That sounded really nice. Too bad he took the wrong step, stumbled over a coiled rope and tumbled down, down, down into the dark sea.

The surface was only safe in the dead of night; that was what Serizawa had been told. Humans were fascinating but wily creatures, not to be trusted. The tales all varied wildly, from humans eating merfolk to seducing them from the ocean’s cool embrace.

Serizawa had always wanted to see one up close but merfolk were supposed to be myths to ones who walked the surface. Thus, he watched from a distance, seeing small creatures toddle on awkward limbs to their progenitors, others holding hands as they walked, still others with backs bent from age as they shuffled along.

He thought humans were neat, if a little goofy in their movements. Like the one who just fell into the water.

The one who wasn’t coming to the surface.

The one who might be drowning.

Serizawa found himself diving into action, his massive tail powering his motions as he moved. He found the human floundering in the water, eyes wide with panic. Serizawa easily grasped the human, pulling him forward into his strong arms.

The human’s eyes had closed. The bubbles ceased flowing from his lips. No, no, no, no!

Serizawa closed his mouth over the human’s, giving him air. It worked, the human’s eyes opening as oxygen hit his lungs. Serizawa did it again, his lips sealed tight over the smaller human, giving him another breath. The human’s hands went from flailing to pressing against Serizawa’s chest. He wasn’t certain if the human was trying to push him away, but Serizawa would not allow it. They were too far below for him to let the human go. He would never make it.

With a swish of his mighty tail, Serizawa launched them up, up toward the shimmering moon dancing above them. The human exhaled, some bubbles escaping his mouth. Serizawa bent forward to give the human another breath but this time, his tongue accidently dipped inside the human’s mouth.

The human jolted in his arms and Serizawa, oh, he realized he should not have done that. The inside of the human’s mouth was salty, bitter, smooth and Serizawa had never tasted something so interesting. He wanted more. They broke through the wake, the sea splashing around them as Serizawa treaded water.

The human could breathe on his own, but Serizawa wouldn’t let him try. Not yet, not when his tongue had new sensations to explore. Not when the human was responding, not when the human’s tongue stroked against his own, not when-- The human finally jerked his head away, eyes a little wild. His golden hair was a messy halo about his head. “I must be drunk,” the man said. “There’s a hot guy making out with me.”

“You think I’m attractive?” Serizawa asked. He found the idea pleasing.

“Sure,” the human said. Then his eyes glazed over. “I think I’m gonna barf.”

One violent expulsion to the side and a discreet swim back to the shoreline later, Serizawa reluctantly set the human in the rocky shallows.

The man stood up, revealing his strange limbs covered in gray fabric and black foot coverings. At least, Serizawa thought they were feet. His knowledge of human anatomy was very limited. As the man turned away from him briefly to reveal a pair of small nicely rounded protrusions Serizawa found himself wanting to rectify that.

The human looked at Serizawa as best he could while being both intoxicated and in the dark. “Is that a tail?” the man asked.

“Yes,” said Serizawa. “I’m a merman.”

“Huh,” the man muttered. He plopped down on the rocks. “Who’d have thought?” The human looked suddenly wistful.

“Are you all right?” Serizawa asked.

“Hmm?” the man was slapping his hand against his ear, presumably to get some errant water out. “Yeah, I guess. I mean, tonight kind of sucked but I met a merman.” He smiled and that was a lovely sight, despite the man’s rumpled appearance.

“My name is Serizawa Katsuya,” the merman said on impulse.

“Reigen Arataka,” the human said. “I guess I should thank you for saving my life. I wasn’t planning on drowning tonight.”

“That’s good.” Serizawa wanted to keep Reigen talking but he didn’t seem to be in any state to. There was so much that Serizawa wanted to know about the surface world and about the human in front of him. He might never have another chance to have his curiosity satisfied.

“Is there anything I can do for you, since you saved me?” Reigen asked.

There was Serizawa’s opening. “Come back here tomorrow at this time,” he demanded.

Reigen looked surprised at the request. “What?”

Remembering a bit of advice from one of his school, Serizawa gave the human his most threatening glower. “You’ll meet me here tomorrow night,” he growled, “or I’ll go to the surface world to find you.”

The human squeaked in shock. “Okay.”

Satisfied that his threat worked, Serizawa smiled at the human. “I’ll see you tomorrow then.” He swam away, looking forward to their next encounter. Back on the shore, Reigen stared at the majestic creature as he disappeared into the black water.

“I am so drunk,” Reigen muttered.

Chapter Text

He couldn’t believe he was doing this. There was no way that he had met a merman last night. He had just been drunk and fell into the water. It couldn’t possibly have been real.

It didn’t explain why he had accepted overtime so staying late would seem reasonable. Or why he was making his way to the dock in the dead of night or—


Reigen jerked his head toward the noise. There, down on the shore, was the man or rather merman he had met last night. He wasn’t crazy. Reigen felt a bubble of excitement in his chest. It was all real.

He carefully climbed down to the water, picking his way through the rocks in his dress shoes. Serizawa waited for him; his human half beached on the shore. He stared up at Reigen with unreadable eyes, his dark hair shining in the light of the moon. His arms were big, just like the rest of him. The merman’s voice was soft, “You came.”

Reigen gulped. A guy who was half fish should not be so damned attractive. Why couldn’t he have been rescued by an ugly merman and save himself some embarrassment?

“Yeah,” Reigen scratched the back of his head. “You did technically threaten me if I didn’t.”

The merman had the grace to look ashamed. “Uh, sorry about that. My school can get a little rough.”

“Your school?” At first Reigen thought Serizawa meant the kind with desks and teachers until the merman continued.

“There’s six of us,” Serizawa said. “Most merfolk keep to themselves but some will form small schools, the Ultimate 5 is one of them.”

“Why is it called the Ultimate 5 if there are six of you?” Reigen asked.

“Because the Chairman is our leader,” Serizawa answered. How this was supposed to answer Reigen’s question, he didn’t know.

“So, now that I’m here what do you want to do?” Reigen asked.

The merman smiled, as if waiting for this opportunity. “Come swim with me,” he said.

Reigen blinked. “You know I nearly drowned last night,” he said, gesturing to his business suit, “and I’m not exactly dressed for it.”

A mighty tail slapped against the water, emphasizing his size and strength. “I wouldn’t let anything happen to you,” Serizawa promised.

Go night swimming with a merman or sit on the shore like an idiot? It took Reigen approximately two seconds to start stripping off his clothes. What else was he going to do tonight: watch bad tv and think about how lonely and crappy everything was and how much he hated his job? Nah, this was a much better alternative.

Serizawa pushed himself off the shore and bobbed in the water, just watching Reigen. The salesman almost considered making it a show, but decided against it. He didn’t want to mistake idle curiosity for something more serious. Especially since he was curious about Serizawa and didn’t want to scare him off.

“What are those?” Serizawa asked, pointing at Reigen’s chest. The salesman had just unbuttoned his shirt and was shrugging it off.

Reigen glanced down. “Oh, those are nipples.” He looked up at Serizawa’s broad chest and was startled to find that the merman had none. What else was different, other than the tail and the gills and--

Serizawa tilted his head. “What are they for?”

“On females they produce milk for young,” Reigen said, “and guys just kind of have them, I guess. One of those things that just haven’t evolved out.”

The merman ran a finger up the tip of his own ears, pointed and elongated like fins. “Like these,” Serizawa muttered.

The salesman shrugged; he was just as clueless about merfolk anatomy as Serizawa was about his. “Sure.”

“Can I touch them?”

Reigen bit the inside of his cheek. Serizawa just wanted to learn about humans, it didn’t mean anything. “Okay,” he agreed. He stepped out of his pants and waded into the water. The only protection he had against the sea was his boxers and that didn’t offer much. His feet could still touch the bottom as the waves gently rolled against his belly.

Serizawa came forward, his face the picture of innocence as he reached out his right hand to cup Reigen’s chest. Reigen nearly fainted just looking at the size of it. Serizawa’s palm gave a quick squeeze to the pec before moving slightly to give the merman a better look at Reigen’s naked chest. A massive thumb flicked against Reigen’s nipple. The salesman shivered at the sensation.

Then Serizawa’s thumb circled the little pink bud, his dark eyes intent as he watched it harden. “Hmmm,” the merman murmured to himself, his other hand coming up to mirror the motion on Reigen’s other nipple. Soon, there were two little hard buds for Serizawa to play with.

God, Reigen had forgotten how sensitive he could be since most of his dates had never bothered with them. Serizawa’s soft touch was going straight to his groin. Then the merman gave them a slight pinch.

It was too much. “Okay, that’s enough,” Reigen snapped, his face red.

Serizawa’s fingers stopped, but his hands did not move. “Maybe they do serve some other purpose,” he suggested. It was only then that he removed his hands from Reigen’s body.

The human looked away. That had sounded an awful lot like flirting. “You said you wanted to go swimming,” he said, changing the subject.

“Yes.” Now Serizawa sounded reluctant about his own plan.

“How do we do this?” Reigen asked, “do I cling to your back or what?”

Serizawa flicked his tail, pushing out into deeper water. “Come out here, we’ll figure it out.”

Cheeky merman. Reigen followed, not nearly as graceful as a creature literally built for the sea. Once his feet could no longer touch the bottom, he was forced to tread water. Serizawa swam around Reigen, as if trying to figure out a method based on the human’s strange limbs.

Suddenly, Serizawa moved behind Reigen and scooped the human up. Reigen squawked at the indignity. “What are you—”

The merman lay on his back, floating in the sea with Reigen laying on top of him. He cradled the human’s back against his chest so they could both stare at the moon. Reigen recalled seeing mother otters carrying their young this same way, maybe that was what inspired the merman. “Don’t know if we’ll get much swimming done this way,” Reigen joked.

A chuckle rumbled against Reigen’s back. “It’ll do,” Serizawa said.

They floated in the dark ocean, chatting about everything and nothing, just enjoying the night and each other’s company. Finally, Serizawa asked, “Do you have a mate?”

“Hmm,” the question took Reigen by surprise. “No, I’m not seeing anyone.”

Serizawa made a strange sound Reigen couldn’t identify. “So, if I made off with you,” Serizawa whispered, his arms tightening across Reigen’s chest, “would anyone come looking?”

That sounded like a threat. Reigen tried to jerk out of Serizawa’s arms but the merman wouldn’t let go. “Sorry, sorry, sorry!” Serizawa sounded completely panicked. “Stop struggling, I didn’t mean to scare you.”

Reigen thrashed violently, falling into the water. He sputtered at the surface before Serizawa grabbed hold of him again. “Please stop,” Serizawa pleaded. He looked absolutely miserable.

“What was that?” Reigen asked, livid that their nice night had been ruined.

“I—I just think you’re neat,” Serizawa said. “And I want to see you again. Please don’t be mad, please.”

The human couldn’t help himself, he burst out laughing. “Oh my god,” he wheezed, “were you trying to ask me out on a date?”

“What’s a date?” Serizawa asked.

Reigen sighed. He guessed that cultural differences were just going to be a part of well, whatever this was. “I’ll explain on the way back to shore,” he said.

“Will you let me carry you?” Serizawa asked.

“Yes.” Reigen didn’t think he could talk and swim anyway. He allowed himself to be cradled again, but this time Serizawa’s arms hung loosely around his waist. It was a small gesture to appear less threatening and Reigen appreciated it. So Reigen told Serizawa about the human concept of dating, the merman listening intently all the while.

“I mean, we can’t do most of that stuff since you’re in the ocean but we can improvise,” Reigen reassured the merman. The moon was far away now, it was time to go. He rolled off of Serizawa’s stomach, his feet firm on the sand.

“Okay,” Serizawa’s voice was small. “When can I see you again?” It seemed the merman realized that demanding a particular date this time would be unwelcome.

“I’m off in a few days,” Reigen said. “I’d like to spend some time with you in the sun, really get to know you.” Honestly, he just wanted to get a good look at the merman; the moonlight could only reveal so much.

Serizawa frowned. “We couldn’t meet here then, too many people.” The merman looked a little frightened. “I can’t be discovered.”

“Right,” Reigen couldn’t believe he hadn’t thought of that.

“There’s a beach to the south where no one goes,” Serizawa said. “There’s no pier but you should be able to get to the water.”

Reigen thought he knew the place. It was kind of a dump which is why people didn’t go there. He’d bring a picnic or something. “Okay, in two days’ time I’ll meet you there,” he promised.

“That’s fine.” Serizawa made no motion to leave.

“What?” Reigen asked.

“Can I--can I kiss you?” Serizawa asked. They had discussed the concept earlier while floating on the waves.

“Well, if we’re going to be dating then of course,” Reigen rambled. He couldn’t believe this was happening, he couldn’t—

Serizawa’s broad hand cupped the back of his head and tugged Reigen forward. The human melted into the kiss; the merman’s tongue was greedy in its exploration. Reigen wanted to stay and just let this creature do what it wanted to him, let Serizawa’s hands roam all over him and touch whatever he fancied. He had to leave before he did something stupid. He pulled away. “Goodbye,” Reigen squeaked before gathering up his clothes and running.

He could feel Serizawa’s dark gaze bore into his back. The wind rushed into his lungs, cooling the water on his skin. This was madness, total utter madness. What would his coworkers say, what would his parents say?

The blonde laughed to himself as he struggled back into his clothes. God, he had never felt so free.

Chapter Text

Serizawa never thought that his curiosity about humans would be satisfied in such a manner. That he would get this up close and personal with a human, that Reigen would allow him to touch, to taste, to plunge his tongue into Reigen’s most private place and spread him open with his fingers while Reigen’s strange appendages twitched on the sand.

To be fair, the date had started out innocently. Reigen had found the secluded beach with no problems and had brought some strange objects he called a basket and a charcoal grill. The grill turned out to be very useful since Serizawa had captured some shellfish from the ocean floor. He had hoped such a gift would impress the human and was gratified at Reigen’s genuine appreciation.

Serizawa was further gratified when he saw what Reigen did to the shellfish on the smoking fire. He had never seen such a thing before and when he was offered a hot scallop, the merman nearly moaned at the flavor. Raw was one thing but charring the flesh did something that Serizawa had never thought possible, it made it better.

They gorged on the fruits of the sea and land, chatting all the while. Serizawa spoke of his home under the water, a little cave he shared with the other Ultimate 5 while Reigen told him about his “job” selling something called a “water cooler” and that it was “the most soul-sucking thing” Reigen had ever done.

As they talked, Serizawa got his first full look at the human. He was not in the gray garments but something shorter and more colorful. Reigen had described them as a t-shirt and bathing suit. The human sat under an umbrella as they spoke to stay out of the sun. “I get burned pretty easily,” Reigen had explained.

Serizawa’s skin didn’t allow for such a thing, he felt sorry for the human. The hot sun also meant that the t-shirt was staying on. He wanted to see Reigen’s bare chest again. The little pink nubs were strange, but there was something tantalizing about the way they had reacted to his touch, and Reigen’s sudden shyness. He wondered if they would harden just as quickly with his tongue, or even faster. Could he get the human to moan for him?

Yes, Serizawa was long past the realization that his interest in Reigen and humanity wasn’t merely scientific. There was an exoticism to the human form, to the way those strange legs attached and separated. He wanted to know what was so important between them that Reigen kept that area hidden even if he stripped off his other garments.

Was that where the human hid his reproductive organs? Did Reigen have an ovipositor like him? Did he have some other parts? Would he allow Serizawa to examine them, to penetrate—

“Are you listening?” Reigen asked.

Serizawa’s filthy thoughts scattered to the high seas. “I’m sorry, I was remembering how tasty the scallop was.” A complete lie, but he didn’t think Reigen would appreciate Serizawa’s inner monologue.

“Did you want to go for a swim?” Reigen asked. “I can slap some sunscreen on and we can go out.”

It was a thought. At least that way the shirt would come off. “Okay,” Serizawa agreed.

Reigen stayed under the umbrella and pulled the t-shirt off over his head. There they were, pink and flat but Serizawa knew that a little stimulation could change their shape. If he was lucky maybe Reigen would let him play with them again. Then Reigen turned around, bending over a bag, sticking his rump in the air. The bathing suit had slipped down just a smidgeon to reveal the top of a crack.

A crack?

“What’s that?” Serizawa asked.

A blonde head looked back over his head. “What’s what?” he asked.

The merman pointed straight at Reigen’s ass. “What’s the split there?”

“Oh,” Reigen reached a hand back and tugged the suit back into place. “That’s just the top of my ass.”

“Ass?” Serizawa asked again. Hopefully this line of inquiry would turn out as well as the one about Reigen’s nipples.

Reigen sat back on his heels. He started slathering a white liquid all over his skin. “It’s another name for butt, buttocks, bottom, rump—” he started listing synonyms.

The merman was puzzled. “Why so many words for the same thing?”

“Humans find our butts inherently funny,” Reigen said with a shrug. He had moved on from rubbing lotion on his top half to his legs.

It was a dangerous question to ask but Serizawa felt the risk was worth the possible reward. “Can I see it?”

Reigen’s hands paused on one of his calves. He slowly raised his head, appraising Serizawa. “You want to look at my ass?”

The merman schooled his face into the same expression that had allowed Reigen to touch him before. “Please.”

Reigen’s head darted around, as if looking for hidden spies.

“There’s no one here,” Serizawa said. “We are completely alone.” Even if it wasn’t about the risk of discovery, Serizawa found that he wanted this particular experience all to himself.

The human lowered his eyes, took in a deep breath and lowered the suit. “Ass” sounded like an ugly name for a body part that interesting. Two rounded protrusions, pale like their owner with a distinctive part in the middle.

He had never seen anything like it before, Serizawa wanted a better look. “Can you move closer?” he asked.

Reigen sighed and wiggled his way toward the water, placing himself just within lunging distance of the merman. Serizawa’s powerful arms lifted himself further out the sea, beaching his front on the warm sand. Now his hands could reach their goal.

The warm skin felt amazing against his sea cold fingers. The soft globes of flesh fit perfectly in his palms. Reigen’s breath hitched. “Um, that’s a little personal,” he whispered, but he didn’t move away.

Serizawa’s thumb dipped into the crease, feeling nothing but smooth skin. Reigen kept perfectly still until the thumb pressed against a rougher texture, something that felt like a hole. It was just below the protective bunched line of the swimsuit, out of Serizawa’s view. He very much wanted to see this mysterious space.

“Reigen?” he asked into the human’s ear.

“Yes?” the answer was breathy, high pitched.

Serizawa pressed his lips to the nape of Reigen’s neck, enjoying the smooth surface there as well. It tasted faintly of the lotion and the salt of human sweat. “May I please see it?” He could feel his own body releasing a slippery secretion on his tail, one used to ease friction during mating. Oh, by the wonders of the sea, please let Reigen have compatible parts.

The human’s skin was flushed, not from the sun but from Serizawa’s attention. Reigen turned his head slightly, one of his brown eyes meeting Serizawa’s. “Okay.” He eased the bathing suit off his strange appendages. With the way he was sitting, Serizawa had an unobstructed view of the rounded globes, but not the space between them.

The pads of Serizawa’s fingers were smooth but he had to be careful with the back of his hands. He didn’t want to hurt Reigen, he just wanted to explore. His palms cupped Reigen’s bottom and lifted, forcing Reigen up onto his knees. Reigen had a weird wrinkled tube dangling in the front, something Serizawa would have to investigate later. But now, he had to find the hole he felt earlier. The pads of his fingers parted the globes and there it was, dusky pink and small.

He had an idea what it was for with the way Reigen trembled, but he wanted the human to say it. “What is it?” Serizawa asked.

Reigen stared up at the sky, unable to meet the merman’s eyes. “Uh, that’s the anus. It’s used primarily for,” he searched for the words, “waste elimination but in some contexts humans also um,” Reigen couldn’t continue.

Serizawa nodded, it was like the cloaca then, it served multiple functions, like mating. It looked clean and inviting. Serizawa dove in without further invitation. Reigen cried out as he was breached with the merman’s tongue. “Thank god I showered,” the human moaned, struggling to stay upright.

The merman noticed and pressed a hand on the dip of Reigen’s back, in the place just before it curved into the backside with which Serizawa was getting acquainted. “You can lay down if you want,” Serizawa offered. Reigen obeyed, sprawling onto his front into the warm sand and letting Serizawa have his way.

The merman was happy to take advantage. If Reigen’s nipples were sensitive, this place drove him mad. It tasted different than the human’s mouth, but Serizawa didn’t mind. It had its own pleasures, most of them in Reigen’s responses, in his moans and babbling talk. If he liked the merman’s tongue this much, maybe he would like the ovipositor better.

As tempting as it was, Serizawa refrained. Partially out of shyness but mostly because he knew that even unretracting it from his body at this moment would make him release. The organ was sensitive on the best of days but just the very idea of mating with the human, of this tight little hole engulfing him, brought him close to eruption.

Reigen rolled his hips back onto Serizawa’s face, hair from his nethers brushing against the merman’s chin. Serizawa wondered if the human could take more and used the pads of his fingers to spread Reigen’s hole so he could dive deeper. His tongue caressed the human from the inside, mimicking what he wanted to do someday with a larger organ.

Reigen shouted, his hips jerking violently. He humped into the sand, warm grains sticking to his front. The human’s hand came back, his fingers threading through Serizawa’s curls. “No more, please,” he murmured. The lazy grin on Reigen’s lips spoke volumes.

Serizawa had just pleasured a human. His own organ twitched in response, releasing his seed into the water. Disappointed at his own lack of stamina, Serizawa resolved to do better. If he were to fully couple with the human one day, he wanted it to last.

Chapter Text

There was something surreal about sitting in his crappy cubicle making phone calls, closing deals, starting new accounts and knowing that he was fucking a merman. That everyday life still happened: chatting around the water cooler, trying to keep up with the latest office gossip to avoid any social minefields and just, in general, working. Then Reigen would escape from that drudgery for a few hours to spend time with the most interesting person he had ever met. And, on occasion, they would end up fooling around.

At least Reigen had something to look forward to now. Loneliness didn’t seem to creep up on him in the same way, but there was still a lack of something. It was not Serizawa’s dick, as much as Reigen joked about it. The merman had seen his penis and freaked out for a solid hour before he could be convinced it was safe. Apparently, sticking his tongue in Reigen’s ass two seconds after seeing it was one thing, but a fully functional human cock was another.

Once Serizawa got over the sight, he started playing with it like he had Reigen’s nipples. It wasn’t too long before he was shoving it in his mouth and fingering Reigen at the same time. He got off on the idea of Reigen’s dick getting hard being a sign that Reigen was aroused. Serizawa also enjoyed the flavor of Reigen’s spend, swallowing it with borderline greed. That was also when Reigen figured out that oil-based lube would be the best thing to prevent chaffing. They weren’t using condoms, Reigen wasn’t sure that they would fit over whatever Serizawa was hiding anyway, so using oil was fine. At least he assumed it was since he didn’t even know the general appearance or size of Serizawa’s mystery organ.

However, no matter how many times Reigen asked about it, Serizawa said he wasn’t ready. He was self-conscious about his stamina; thus, Reigen had never seen it. He knew that it was there, Serizawa referenced his “engorged ovipositor” often enough. So, the salesman had to be patient. Good things come to those who wait, and all that.

Little did he know, that next afternoon the wait would be over. Serizawa perched on a rock at the edge of the shore. His eyes were intent as Reigen approached. “I’m ready,” he intoned, very serious.

“Ready for what?” Reigen hadn’t even had a chance to set up his little camp.

“To show it to you,” Serizawa said.

Reigen did not have to ask for clarification. He dumped his supplies into the sand and marched over to the merman, stripping off his shirt as he approached. Months of anticipation had led to this; he wasn’t going to let a few clothes get in the way. Shimmying out of his swim trunks, he plopped down next to the rock stark naked. “All right,” he said.

Closing his eyes, Serizawa exhaled and the slit in front of his groin opened. Reigen loved Serizawa’s tail, it was nothing like what he had expected. When they had met in the middle of the night, Reigen couldn’t appreciate its girth and mottled coloring. It looked nothing like the mermaid tails in cartoons but rather a mighty shark growing from Serizawa’s torso. These meetings during the day allowed Reigen to admire it all he wanted, and now Serizawa was showing him its last secret.

It grew out from the slit, a multi-colored protrusion with ridges at the base, just as beautiful and exotic as the rest of Serizawa’s tail. It looked almost like a tie-dyed croissant from a specialty bakery. Reigen reached out to touch it. The texture was not what he expected. “Kind of squishy.”

Serizawa hissed, grasping Reigen’s wrist. “Please don’t do that.”

Eyes wide, Reigen drew back his hand. “Did I hurt you?”

“No,” Serizawa insisted, “it’s just very sensitive. Even being in the open is difficult.” The merman’s face was flushed just from the innocent touch.

Now Reigen was uncertain. “What do you want me to do then?” If it was that sensitive--

Serizawa released his wrist. “Prepare yourself and get in the water.” He slid off the rock, moving out of the shallows.

That was unusual, Serizawa loved playing with Reigen’s ass but he must really be on the brink if he wanted Reigen to do it. The human routed through his bag and found the oil. He would make this quick, he was just as eager to try Serizawa’s dick as the merman was to use it. The first breach made him puff out a little air, maybe he should go a little slower.

Reigen looked out into the water just in time to see Serizawa duck his red face under the waves. It was tempting to spread his legs, let Serizawa see the hole he wanted so much swallow Reigen’s slick fingers and work himself open but that seemed cruel at the moment. He would have to save the idea for a later date.

When he was ready Reigen followed Serizawa out into the water. He did a few breaststrokes into the sea before Serizawa indicated some rocks a little further out. It took Reigen longer to get there than Serizawa, but the merman waited for him with hungry eyes. “You can hold on here,” Serizawa pressed his hand against a rock smooth from the ever-crashing waves.

Reigen had never done this in the water before, he had never even screwed in a bath. This was going to be a new experience in more ways than one. He couldn’t touch the bottom, his hands clung to the smooth rock in front of him, his legs kicking slightly to tread water. He felt the merman press against his back, a solid, unmoving presence. A pair of broad palms settled on his hips and Reigen stopped moving his legs. Serizawa leaned over his shoulder, his chest rumbling. “Just like that,” he murmured.

Reigen felt Serizawa’s dick, the squishy tube of it press briefly underneath his balls before traveling back and up, seeking entrance. The tip pressed right up against him. “Tell me when you’re ready,” Serizawa said. “I can’t stop once I’m inside you.”

Reigen shuddered. With anyone else that would have been terrifying but he wanted this, wanted Serizawa. He spread his legs and rolled his hips, allowing the merman to sink inside. It took only a few seconds for Reigen to realize this is not what he was used to. The appendage was thick, yes, but spongy, filling him up in a whole different way.

It was less hard then flexible, almost having a mind of its own. Then he felt the ridges, soft but immobile at the base. Serizawa pushed forward on Reigen’s hips and there was no movement. He was locked in until he finished. Even if Serizawa wanted to pull out, he couldn’t, he had to cum first. He had to cum inside Reigen.

The human squirmed on the cock filling him; damn it, that shouldn’t sound that hot. Condoms were a staple of Reigen’s sparse sex life, he didn’t want any of his stupid one-night stands finishing in him but with Serizawa it was different. Serizawa was kind, funny, sweet and stupidly hot. He wanted Serizawa inside him, he wanted to feel all of him.

“The number of times I’ve released my seed into the sea shames me,” Serizawa whispered, the hands on Reigen’s hips shifted to cup his ass. “It should have been here inside you.”

The merman’s tail didn’t move, but the cock inside Reigen did. It shrank and expanded, simulating a thrusting movement. Reigen didn’t know what to do with himself, there was nothing to really push back against, he just had to take the squirming appendage, had to let him stroke him from the inside.

“You feel so amazing,” Serizawa panted in his ear. “Better than I imagined.” His palms roughly squeezed the globes of Reigen’s cheeks. “These are so weird but I can’t stop touching them. So smooth, so round.”

It was bizarre hearing the merman talk about his ass like that but with that squishy dick filling him in all the right ways he didn’t care. Serizawa could write a sonnet about his ass and Reigen would just nod in appreciation as long as that cock kept shifting further inside. “Right there, almost there,” Reigen murmured. Serizawa’s cock pulsed again right where Reigen needed it. “Yes, please!”

Then Serizawa’s hands moved up to pinch his nipples. Reigen yelped, squeezing involuntarily. Serizawa moaned. “Keep doing that,” the merman ordered.

The human didn’t know if he could; he was squirming his hips as Serizawa’s cock kept expanding and contracting in that damned spot and the merman’s fingers were teasing his nipples like he could make Reigen cum from that alone. Sex with Serizawa was always an adventure but this was blowing all those other encounters away. How could he be satisfied with anyone else when this amazing cock wanted to fuck him?

Serizawa’s fingers flicked at his nipples at the same time and Reigen was done, his own neglected dick twitching in the cool ocean water. The merman hummed, his cock expanding inside of Reigen, nearly filling him to capacity as he came. Ridges kept every precious drop in place, none escaping. Reigen’s hole was for Serizawa’s use, for his personal pleasure. As long as his seed was inside, Reigen belonged to him.

The merman’s hands fell from Reigen’s nipples to curl around the man’s chest. Serizawa didn’t want to withdraw just yet. He rolled onto his back in an otter glide, taking the human with him. They were locked together now, until Serizawa decided they were done.

In the peaceful waves of the sea they could enjoy the afterglow, Serizawa’s ridges helping to keep Reigen in place. “Did you like it?” Serizawa asked, kissing Reigen’s temple.

“Yeah,” Reigen replied, turning his head to press his own sloppy kiss onto Serizawa’s cheek. The merman’s dick was still full inside him, he liked the feeling. It was as if Serizawa didn’t want to let him go. It was nice to still be wanted, still be desired even after the act. “Are you happy?” he asked, needing to know.

An innocent question and one that Serizawa had never seriously contemplated. Life in the sea was what it was, survival was always at the forefront. Happiness was a rare condition, one to be savored. To have someone ask him that, let alone a human should have been preposterous. From Reigen though, it seemed like the only question to ask.

“Yes,” Serizawa said with a soft smile. “I am happy.”

Chapter Text

Disquiet is inevitable when you realize that the life you lead is not the one you want. That somewhere out in the wider world is opportunity, if only you have the courage to take it. In a small cave at the bottom of the sea, disquiet settled over Serizawa Katsuya. The others in the Ultimate 5 slumbered easily, tails twitching during particularly vivid dreams. The sounds of their enthusiastic sleep washed over Serizawa but he took no comfort in it, just a vague annoyance.

His school was one formed for protection and food scavenging. They had little loyalty or need for companionship outside of their immediate circle. For a time, it had been enough for the merman but now that he had met Reigen he yearned for a different type of life. A life of laughter and intimacy, a life he was just getting a glimpse of.

Could he abandon his fellows for that?

“Can’t sleep, Serizawa?” the authoritative voice was quiet but would not be ignored. It was Suzuki Touchiro, the school’s leader. Slender but imposing with a tail featuring the distinctive gray and white coloring of a Great White, Suzuki held sway over mermen bigger than himself through sheer force of will. Serizawa sprang to alertness.

“Mr. Chairman,” he answered. When he saw the others stirring, he recognized just how loud he was being. “Yes, Mr. Chairman,” he repeated quietly, as if that canceled out the previous shout.

“Swim with me,” Suzuki ordered, leading Serizawa out of the cave.

Serizawa looked back over his shoulder. The only merman who took any notice was Minegishi, who briefly woke then buried himself under his distinctive pile of kelp. His yellowish tail stilled as he drifted back into sleep.

When they were out of hearing range of the others, Suzuki halted. He cut right to the heart of the matter. “You’re still sleeping with the human?”

“I—’ Serizawa allowed himself a pause to collect himself. “I don’t see how that matters.”

Suzuki was blunt. “Your proclivities endanger the school, Serizawa. However,” he conceded, “the fact that a swarm of humans have not descended upon us means that he has kept you secret. He at least values your safety.”

Serizawa thought Reigen valued a lot more than that. “Anything else, Mr. Chairman?” He did not wish to continue this conversation if it was just going to be more criticism.

“You have been distracted,” Suzuki said, “and distraction can also endanger the school.”

Serizawa had enough of this. It was late, he was tired and he wouldn’t see Reigen for another two days. “What do you really mean to say?”

The leader of the Ultimate 5 raised an eyebrow. Serizawa was not usually one to question him. The human’s influence was stronger than he thought. “You need to make a decision,” he told Serizawa, “about what you actually want.” He placed a hand on his subordinate’s shoulder. “Has he asked you to leave the sea?” he asked in all seriousness. “Has he asked you to give up your tail?”

“What?” Serizawa was horrified. “No, Arataka hasn’t said anything like that.” The biggest demand Reigen had ever made of him was for cuddling which Serizawa was more than happy to do. Besides, Serizawa had no idea how one would even go about discarding their tail.

The older merman’s lips thinned. “He might,” he said. “You need to consider all of the consequences. If you chose to be with him, there will be no place for you in our school.”

Which meant no protection, which meant that Serizawa would have to stake his own territory for feeding. If there was trouble or a dispute he would be on his own. It was a terrible risk.

Suzuki understood the silence. “This decision is a weighty one,” he said, “it shouldn’t be made lightly. I will give you time.”

Time that Serizawa was going to need. “Thank you.” He watched Suzuki swim away out of the corner of his eye. The Chairman was right, he was going to have to consider all of the consequences. If he did leave the school for Reigen, what would that actually mean? What could their potential life even be like?

There’s an old saying, “A fish and a bird may fall in love, but where will they build a home together?” If Serizawa had any knowledge of it, he would have felt its message all too acutely.


Morning meetings were the worst, followed by afternoon meetings and evening meetings. Okay, meetings in general just sucked; especially the ones led by blowhards with their heads so far up their own—

“And with Accountants, Inc expanding into Seasoning City,” his manager droned on, “they’ve decided to bring in a few of their representatives to oversee our installation of their new water coolers.”

What? The pencil Reigen had been fiddling with slipped out from between his fingers with a loud clatter. A few of the other salesman looked at him with disgust, but Reigen ignored them. This was actually important.

“Among the reps from Accountants, Inc are—” the manager started listing names, names that Reigen was only vaguely familiar with.

Reigen prayed that Ito would not be among them.

“Ito-san and Hanazawa-san.”

Damn it, damn it, damn it.

Considering how handsy Ito-san was at the last party, Reigen doubted that the man would be professional enough to leave him alone. If Ito-san’s transfer to Seasoning was permanent then there would be no way for Reigen to avoid him. He would have to spend the rest of his life evading come-ons and propositions from an accountant who didn’t know when to quit.

Reigen spent the rest of the day fuming. He was short on the phone, his voice pinched and tight when fulfilling orders. The usual finesse he exhibited had gone right out the window. It was probably the worst day he had on the job since the first one.

He isolated himself at lunch, refusing to deal with office gossip or the petty concerns of other people. The salesman had his own worries.

It wasn’t until he left the konbini with a few too many beers in his bag that he came to a realization: why was he worried about Ito-san making his job suck? Reigen already hated his job. He hated convincing people that his product was somehow superior despite being identical in every way to the competitions’. He loathed his coworkers and their after-work drinking, every report he had to submit was excruciating, every little tick towards his sales goal hollow and meaningless.

Reigen lived in a crappy studio apartment socking away his money for some nebulous future. His coworkers spent their money on frivolous things but Reigen had always been frugal. He had some savings, what exactly was he saving for?

For a car, for a vacation, for a house?

He paused in his tracks; the plastic bag heavy in his hands. A house. It didn’t have to be a big house but it should be by the sea, maybe even connected to the sea itself. His arms broke out in goosebumps.

Maybe the future didn’t have to be nebulous, maybe there was something or rather, someone, to look forward to. Money was a means to an end, not a goal unto itself. What was important was bonds, connections to others. His coworkers were shallow sheep that he didn’t identify with at all. No, he had a gentle giant who spoke of the wonders of the sea, who held the same curiosity for land that Reigen had for the water.

Reigen didn’t need Big Cool Water, he needed Serizawa. The salesman broke out into a run, eager to catch the next subway train. New possibilities churned in his brain, new plots and threads. He needed to get back to that crappy studio apartment to the laptop that awaited him there.

That thin collection of plastics and electronics was his tenuous connection to a future, a wanted future if he was brave enough. He had never thought of that apartment as home but with some effort it could lead him to a real one. A home he wouldn’t have to endure alone, one that could be shared if he only dared.

Chapter Text

Reigen wasn’t on the beach. It was the appointed time and the human wasn’t there. Serizawa felt his heart sink as he approached the rocks. Had something happened? Was there an emergency? Did Reigen not want to see him anymore?

Then he saw the plastic bottle tethered to the rocks. Serizawa grabbed it, unscrewing the lid; he knew it was from Reigen, he just knew it. Inside was a laminated map and a few words: “Meet Me Here.” The spot indicated was about a twenty-minute swim further up the coast to a cove Serizawa had never visited. What was so important there?

Was this some sort of trap? Was this even Reigen’s writing? Serizawa shook off the thoughts, those were Suzuki’s ideas not his. He would go to this place, see what Reigen wanted to show him. The worst that happened was a waste of time and the best, well he didn’t know what the best could mean.

The merman set off, his powerful tail and sonar guiding the way. Since the talk with Suzuki, Serizawa could not stop thinking. What did he really want? He wanted Reigen, he wanted to spend more time with the man, not just the snatches they could steal here and there. However, life in the land and sea were so vastly different. Was it fair to ask either of them to give it up?

Serizawa could not live without his tail, without the feel of the water passing through his gills and if Reigen didn’t have his legs—the merman felt the breath in his lungs turn to lead. He couldn’t ask that of Reigen; he couldn’t ask the man to give up one of the things that Serizawa loved about him.

Were they ultimately doomed to stay apart? What would happen when the winter comes and the water freezes? Would Reigen still come to the beach despite the temperature or would he stay away until the spring? Would Serizawa even want to live that long without seeing him?

Serizawa’s destination was a secluded cove much like the one he frequented with Reigen. Rocky shoreline with a bit of sandy beach, it was nothing special. At least, except for the house.

Two stories of dilapidated wood building that pushed up into the water stood alone. There were no other buildings, no other indications of human inhabitation. Even the single road was overgrown with weeds. The majority of the first floor of the house was open to the sea; Serizawa could swim right in, if he so chose.


Serizawa jerked his head to the sound of the familiar voice. It was Reigen, and he was waving from inside the odd house. “Come on in, the charcoal’s almost ready.”

He could smell it, Reigen’s little portable grill. The merman’s stomach rumbled. He surged through the water toward the house, eager to see what Reigen had in store.

Upon closer examination, the first floor was a dock for boats, so it was more than large enough to accommodate Serizawa. Reigen had set up the little grill next to the water with a pile of food ready to cook. He was dressed as he usually was for their dates, swim trunks and a tee-shirt, but with the cover of the house he hadn’t had to set up his umbrella.

Reigen patted the edge of the dock. “Why don’t you join me, big guy?

Serizawa did not have to be asked twice. He gripped the edge of the dock and, using his large forearms, pulled himself out of the water. The wood groaned beneath his weight.

Reigen raised his eyebrows in alarm, “I’ll have to keep that in mind.”

“What is this place?” Serizawa asked.

“It’s called a funaya. This one’s pretty old but I crunched some numbers,” Reigen rambled, throwing some sausages on the grill. “Since it’s not in good shape I can get it for a song and it’s not registered as historical property so that helps.”

Serizawa watched Reigen’s face as he spoke. The human was visibly excited, his hands gesticulating wildly. “There’s just so many possibilities, renovation or even just tearing it down and starting over,” Reigen said. “I do want to keep this concept though,” he waved at the dock with his tongs, “but maybe expand it to other parts of the house. Not sure if I should keep some living areas on a second story or just make it all one.”

“Arataka,” Serizawa was baffled, the human was speaking so quickly. “What are you talking about?”

“Oh,” Reigen laughed at himself. “Sorry, forgot to actually tell you.” He scratched the back of his head, a tell-tale sign of nerves. “This is our house, maybe, if you want.”

If Serizawa wanted? If he—

The merman slid down back into the water, swimming from one edge of the dock to the other, really looking at the house. It was in terrible condition, but Serizawa still understood what Reigen was trying to say. This could be theirs. THEIRS. Reigen wanted to build a home with him, for him. While Serizawa had just been contemplating the possibility, Reigen had been doing, had been setting plans into motion.

Serizawa was overwhelmed with sudden affection.

“Katsuya?” Reigen asked, looking a little uncertain.

The merman swam back to the human’s side. He raised himself up, his hand grasping Reigen’s calf. “Join me,” Serizawa requested.

“The sausages are going to burn,” Reigen teased.

“You can finish them later,” Serizawa said. He smiled, inviting and gentle. “I’m hungry for something else.”

The human took the hint. He shuffled the meat off the grill onto a plate. “So,” Reigen pulled his shirt off, “I take it that’s a yes.”

“Yes,” Serizawa agreed in a breathy exhale, his hands pulling Reigen toward the water. He loved this man; he wanted this man. He could abandon everything else if he had a place in Reigen’s heart and his home.

“Careful, I’ll get splinters,” Reigen whined, kicking Serizawa off him. He laughed at the merman’s pout, much to Serizawa’s displeasure. Then Reigen stood up and dramatically shimmied off his swim trunks, purposefully turning to show off his ass. The ass that was just out of Serizawa’s reach.

“Why do you bother with clothes?” Serizawa complained. “They get in the way.” Mostly in the way of Serizawa’s gaze and wandering hands.

“Clothes are necessary for human society,” Reigen said. Serizawa knew this perfectly well, but Reigen liked to remind him every once and a while. “Besides,” Reigen continued, sliding into the water, “then everyone else would see me naked too.”

True. Some delights Serizawa wanted to keep for himself. Delights like gathering Reigen in his arms, like swimming with him in the moonlight, like making love in the cool water or on the warm sand. Reigen’s lips were soft against his own, the human’s fingers combing through his hair.

“How do you want me?” Reigen asked.

Anyway, all ways, as many ways as the human would allow. Serizawa ran his hands up those odd legs, the ones that could be bent in different fashions to please him. Legs that could wrap around the merman’s girth, legs that could be pressed back against the human’s chest, legs that could only dangle helplessly as Serizawa took him from behind.

This time, Serizawa wanted to feel those legs around him. He rolled onto his back, one of his favorite ways to carry Reigen, drawing the human up out of the water. The merman grasped Reigen’s hips, adjusting him to sit perfectly over the slit in Serizawa’s tail.

“Is that what I think that is?” Reigen asked.

Serizawa nodded; eyes lidded. “Lean forward.”

Reigen obeyed. His legs were already spread to straddle Serizawa’s middle and leaning forward so their chests could touch exposed his tight little pucker to Serizawa’s questing fingers. The merman slicked them with the secretions from his tail and pushed in. The slick was designed for just this purpose, easing the coupling between mates.

The human kept his breaths even, trying not to betray his own excitement but Serizawa knew better. Reigen’s organ lay thick and hard between them, smearing Serizawa’s belly with his own eagerness. The human’s hips pushed back onto the merman’s fingers, driving them in deeper. It was time.

Serizawa withdrew his fingers and silently commanded Reigen to sit back up. The human sighed as he pushed himself upright. Then Serizawa’s slit parted and Reigen arched his back with a gasp as Serizawa slipped inside the human. Serizawa loved this particular position, it afforded him an unobstructed view of Reigen’s front, the perky nipples and hard human cock. It also allowed him to touch where he wished and observe Reigen’s flushed face as he was ravaged. Sometimes the spread legs would even squeeze around him if Serizawa did something right.

The merman bent upward so he could lick at Reigen’s chest. The pink nipple was firm against his tongue. Serizawa had nothing even remotely like it on his own body. It was so alien but delightful all the same. Reigen let out a high keening noise as he was fucked.

Learning how to deal with his own sensitivity was worth all of this, these moments of being inside the human. Serizawa could still only stand a few licks from Reigen’s tongue but in this, this he could last longer.

If he had one wish, it would be to take Reigen for hours, to truly wear the human out. It was selfish, but weren’t most desires in the end?

The position hurt Serizawa’s back so he had to reluctantly lower himself back into the cradle of the sea. Reigen tried to bounce on Serizawa’s lap, but the ridges kept his movements too small to be satisfactory. He fell onto his front, his mouth kissing Serizawa’s neck. “Please,” Reigen moaned.

“Please what?”

“Touch me, touch me anywhere,” Reigen pleaded, burying his head against Serizawa’s shoulder.

Serizawa was more than happy to oblige; he was having a hard time not finishing inside Reigen’s welcoming body. One hand moved to fondle the blonde’s bottom while the other slid between them to wrap around Reigen’s dick. The human keened again as Serizawa’s clever fingers stroked him. Serizawa had no pride. He didn’t care who came first as long as they both did.

His own cock expanded and flooded Reigen with seed. Serizawa groaned at the effort, glad that, once again, the sea could claim none of this. His spend was all for Reigen, all for the human who made life worth living. Reigen panted at the sensation, not quite over the edge yet but getting there. Serizawa kissed his throat and stroked him through the last of it, grateful for Reigen’s frenzied babbling and declarations: “Fuck me, just like that. Thank you, love you.”

Love, Serizawa thought as Reigen collapsed against him, that was as good a foundation for a future as anything. He wrapped his arms around his human, squeezing gently. Reigen had already started planning and Serizawa had contributed nothing.

The situation could not stand. If this was to be a home, a real home, Serizawa needed to do something for it, but what? He had no currency like the humans, no means to help Reigen with the dream.


Down in the dark there were places human with all their technology dared not go. Places where storms had destroyed ships, consigning their cargos and crews to the depths. Such places existed in the Ultimate 5’s territory, though they remained unexplored. Who knew what treasures lurked hidden amongst the dangers?

Reigen snored against his chest, he would have to awaken soon if they were to eat. However, Serizawa let him sleep a few moments longer while his own mind drifted to the uncharted dark.

Chapter Text

Flags mean little to a creature whose life is spent beneath the waves. Territory is marked in the sea, not by treaties, but by smell and the strength to defend it.

This stretch of the ocean was technically Ultimate 5 territory, but far deeper than they dared to venture. Despite his advanced sensory organs and sonar, Serizawa knew that his greatest enemy would be the dark. He could get lost in the dark. He could be eaten in the dark.

Serizawa had convinced a skeptical Reigen to gift him a light that worked underwater. Its beam would only project so far, but it was better than nothing.

“I don’t know how long the battery life is,” Reigen had told him, “but I made sure it’s fully charged.” He had handed the device to the merman who looked at it like a distasteful plastic bug. “You press this button here.” He had reached over to demonstrate, laughing at Serizawa’s startled reaction. “What do you even want this for?” Reigen had asked.

Serizawa couldn’t even remember the lie, only that it was weak. The human did not question him further but the suspicion in Reigen’s eyes haunted him. If he was successful, Serizawa would more than make up for not telling the truth.

He was at the shelf now, where the water grows black. It is not the True Dark, no merfolk dare go there, for the water grows heavy and crushes the very life out of creatures that dwell closer to the sun. No, but it was still tricky to navigate. Other things lurked down there, unfamiliar things.

Serizawa turned on the light, the beam was narrow. It would have to be enough.

He followed the light down, extending out his sonar to seek his target: the remains of a ship that sank long ago, many decades before Serizawa was spawned. If he could reach it, he hoped to salvage something useful for Reigen. Perhaps the human could sell it like his strange “water coolers” and procure the funds for their home.

Serizawa would not let Reigen be the only one to build their dream.

After about ten minutes, the beam struck a rusted wall of metal, the focus scattering. The ship was massive, broken into pieces by nature and war. A monstrosity of metal and wood, Serizawa could not fathom the hands that had shaped it.

If the merman could read, he would still have not known what the wreck was. It was not a ship native to Japan’s shores but from further north to a place Serizawa would never go. A gash in the side covered with barnacles drew Serizawa’s attention. He sent out a signal, there were large box shaped objects within.

He focused the flashlight on the gash and swam forward, into the gutted ship’s interior. The ship was not designed for comfort, it was a vessel sculpted for battle. Those versed in military history could find beauty in it, but not Serizawa. Even as a member of one of the more vicious schools, violence did not appeal to him. Small fishes swam around him, having built their home in the long-abandoned craft. He could only hope nothing bigger had decided to dwell there.

Serizawa went deeper to a massive door that was partially opened. He used his massive arms to wrench it open just enough to squeeze his body through. There, those were the boxes he had sought.

Long containers of iron, their locks long rusted off awaited him. Serizawa lifted the lid off one, the noise loud even under the muffling effects of the water. The light touched the interior of the container, sending its reflection back to fight the gloom. Serizawa reached out to touch the smooth bar of gold. He wrapped his fingers around it, shocked at the weight. He could possibly carry two at the most.

That’s when he felt the familiar charge of electric impulse down his side, something else was in the cargo hold and it was big. He turned to see the scalloped hammerhead shaking its head back and forth at him, assessing. The shark’s back was bowed, a sign of aggression.

The hammerhead was not hungry, he was not some mindless killing machine, but this ship was his territory and he was letting the merman know it. Serizawa grabbed the two bars and held them out in front of him. His arms sagged at their weight.

The shark’s back leveled out, he was puzzled at the merman’s behavior. Puzzled was still better than frightened or threatened. Serizawa swam backwards, out of the hold, watching the shark the entire time.

The hammerhead watched him retreat; he did not follow.

It wasn’t until Serizawa left the ship’s hull that he felt like he could breathe again. Then he saw the others and held his breath again. It was the Ultimate 5: stern Suzuki, kelp-covered Minegishi, Shibata of the tiger shark’s strength, blind Shimazaki with the mako’s speed and Hatori, the one who was perpetually mocked for looking like a pyjama shark.

“What are you doing here?” Serizawa asked.

“We followed you,” Suzuki said, “making sure you weren’t putting yourself in unnecessary danger.” In the outskirts of the light, Serizawa could see Suzuki’s eyes flash toward the gold. “Did your human tell you to fetch that for him?”

“No,” Serizawa said, he would not have Suzuki speak ill of Reigen. “He knows nothing about this.” He clutched the bars to his chest, juggling the light.

“He doesn’t know that you’re diving through human trash looking for baubles?” Hatori sneered, his striped tail curling around him. He didn’t want any of the small fish of the wreck touching him.

“Not too smart, Serizawa,” Shimazaki chimed in, demonstrating his agility by swimming in circles around the school. He was the only one unbothered by the dark.

Shibata said nothing, his judgement was silent.

“Probably not,” Serizawa agreed, “but I’m not letting him do it alone.”

“Do what?” Suzuki asked.

It wasn’t the ideal time, but Serizawa would have to confess sometime: “He’s building a home for the both of us.”

Suzuki sucked in a hissing breath. “He’s asked you to give up your tail.”

“No,” Serizawa said, “he’s making a home where the house meets the sea.”

Now Hatori’s curiosity was peaked. “How would that even work?”

“Well,” Serizawa wanted to demonstrate but his hands were full. Shibata took the bars from his grip without effort. Using his hands and the light, Serizawa suggested the boat with the dock. “The first story is a dock so I can swim into the house. The place is a disaster but we can rebuild or re-some other word he used.” He was getting flustered. Serizawa had not expected to explain any of this now. He had wanted to gather his thoughts, his arguments.

Suzuki considered this for a moment. “How long will it take him to build?”

“I don’t know, I don’t think even he knows,” Serizawa said.

Suzuki considered for a moment. He snapped his fingers and gestured to the empty-handed members of the Ultimate 5. “Bring up more, we’ll take them to the cave,” Suzuki ordered. They obeyed at once.

Serizawa was stunned. “Why?”

Suzuki took one bar from Shibata’s arms. “You will give your human one of these as a gesture of good faith. If he acts on it, we will give him the others we’ve gathered.” The leader handed the single heavy gold bar back to Serizawa. It was useless to the merman; it could not be bartered for food or for protection.

It could only be used for this. “Thank you,” Serizawa said.

“Save your thanks until after you show your human,” Suzuki ordered. “We’ll see if your fairytale is worth the happy ending,”

The merman’s chest swelled with confidence. “It will be,” Serizawa insisted.

That was when Suzuki granted Serizawa one of his rare smiles. It seemed that, despite himself, the Chairman believed it too.

Chapter Text

The next time they met, it was at their usual beach. Serizawa twitched with nerves the entire time, waiting for the right opportunity to surprise Reigen with his gift. The human was funny and passionate as always, excited about the new possibilities before them. “I’ll have to be careful with timing my two weeks’ notice,” Reigen said. “Don’t want to run out of money before we start construction.” He pulled his knees to his chest.

“The town’s kind of dying so finding work might be hard,” Reigen admitted. “Still, I’ll think of something.” He grinned at Serizawa. “What will you do all day when I’m at work?” he teased.

Just being asked that question made Serizawa’s head spin. Reigen was serious, this wasn’t all a whim. He wanted to spend his life with Serizawa. The merman thought about it. “Swim and find us food,” Serizawa said.

“You catch the best stuff,” Reigen agreed, leaning back on his blanket, hands behind his head.

“Dream about making love to you,” Serizawa added, his hand reaching out to stroke Reigen’s leg, “and then acting on it when you get home.”

Reigen flushed at the sentiment. “You’re too good to me,” he joked.

There was much that Serizawa could not give Reigen, with his body bound to the sea and his love’s to land. He knew this all too well. It was time for the gift. “You should want for nothing, Arataka,” Serizawa said. He pushed himself back into the water.

“Where are you going?” Reigen asked.

“I’ll be right back,” Serizawa said. He ducked under the waves to the crevice where he had hidden his present before their date. It was still there, solid and heavy. Serizawa pulled it out of its makeshift cubby and rose to the surface. With an inelegant grunt, he dropped the bar at Reigen’s feet.

The human could only stare with wide eyes. “Serizawa, is that—”

“It came from the sea,” Serizawa explained, eager to tell his tale, “I found it—”

Reigen placed a finger on the merman’s lips. “I don’t want to know,” he said. The human looked genuinely worried. He kissed Serizawa; the gesture soft. He leaned his forehead against Serizawa’s. “Please don’t tell me you hurt yourself for this.”

“I didn’t.” This was not the reaction Serizawa was expecting.

“And don’t go back to get more,” Reigen pleaded. “Between salvagers and animals and god knows what else—” The human shuddered. “If something happened to you—"

Serizawa couldn’t help the smile. “I won’t,” he promised. The Ultimate 5 had already brought the gold back to their cave, eight bars in total, including this one. He would wait to present the others.

“I’ll have to find a buyer, can’t just wave this thing around.” Reigen attempted to pick up the bar, his eyes boggled at the weight. “Really can’t wave this around,” he muttered. He set the bar down again just staring at the solid gold. “We can meet again at the house in three days, I’ll give you an update on what it’s worth.”

The house, Reigen meant their soon-to-be-house. His hand traced a path up Reigen’s arm to the back of his neck. “Come into the water,” he whispered.

“You know,” Reigen goaded him, with a playful flash of teeth, “you can’t buy my love with shiny things.”

He did know, he knew it with every fiber of his being. Serizawa knew it from Reigen’s smiles, knew it from the stories he would tell, knew it from the dreams he shared with Serizawa in lazy whispers and from the way their fingers intertwined as Serizawa made love to him. From the way he let out his high-pitched whines, from how he moaned for more, from how his tight little hole milked Serizawa dry.

Reigen’s legs wrapped around him, squeezing as Serizawa finished. The human nipped at Serizawa’s chin. “If you keep your dick in me like that, I’ll get excited,” Reigen teased. He squirmed to emphasize the point. “Then I might just have to let you fuck me again.”

The idea was very intriguing, though Serizawa might have to temporarily withdraw to clean out some of his cum. He went a little light-headed at the thought of filling Reigen up again. “Do you promise?” Serizawa asked.

The human squeezed his legs around Serizawa’s middle. “I wouldn’t say it if I didn’t mean it.” Reigen was not just talking about sex.

Merfolk were not built for multiple orgasms, but Serizawa accomplished a miracle that day and took his lover for a second time. It was slow, deliberate, meant slowly to maintain their connection for as long as possible. Serizawa’s sensitivity usually leant a franticness to their coupling, but his will was strong today.

Once they lived together, they could make love whenever they wished, they could live how they wished. It was this fantasy that carried him through, that let him wait until Reigen came undone beneath him, that gave him the patience to hear, “Cum for me, big guy” before letting go.

Three days later, Serizawa found Reigen waiting for him in the dilapidated house by the sea. The human held his laptop, a device he had introduced to Serizawa before to demonstrate cat videos or as Reigen had called them, “The reason the Internet was invented.” Reigen’s face was radiant.

“I take it you found a buyer,” Serizawa said once he was close enough.

“Yes! I can’t meet with them for a few weeks, but we can still make plans.” Reigen plopped on the dock, propping the laptop up so Serizawa could see. “I’ve been finding some pictures online of houses and ideas, I want your opinion.”

He scrolled through multiple photographs of things like docks and features of human homes that Serizawa couldn’t comprehend: things called kitchens and bathrooms and patios.

“I don’t cook often but I’ll need to do it more when we live out here. Town’s a little far out and if I can’t eat with you what’s the point?” Reigen rambled on and on, in words that came out faster with anticipation.

Serizawa was overwhelmed with information. A distraction would be necessary to refocus. “Will it be enough?” Serizawa asked.

Reigen appeared thrown by the question. “Yes,” he answered, closing the laptop. “The bar’s worth over 54,000,000 yen.” The number meant nothing to Serizawa, but from the way Reigen clung to him, his eyes wet with tears, it moved Reigen greatly. “We can build our house,” he said. He kissed Serizawa’s cheek. “We don’t need a big place,” Reigen insisted, “just a place meant for us.”

Us. Serizawa liked the sound of that.

“We can even hire an architect, make this place right,” Reigen said. Serizawa had heard the word only once; he had a vague idea of what Reigen meant. “I’ll still need to work,” Reigen explained, “but I don’t mind, it’ll keep me busy.” He took Serizawa’s hand, his thumb rubbing into the merman’s palm. “I’ve dipped into my savings; I’ve already made the offer.”

“’Taka.” Serizawa’s chest felt tight.

“This place is an akiya so it’s not a whole lot of money,” Reigen explained. “I might have to eat more instant ramen than normal—”

“That won’t be necessary.”

Reigen jumped to his feet at the unfamiliar voice. It was Suzuki and the rest of the Ultimate 5; Serizawa was irritated at being followed.

“Mr. Chairman,” he greeted his superior.

“Serizawa.” Suzuki eyed Reigen, scrutinizing his casual attire. “Human.”

Reigen refused to be thrown by this, he put on his best game face: “Reigen Arataka.” He too made a show of looking over the Ultimate 5. “I assume you are Serizawa’s school.”

Suzuki’s lips twitched. “He’s seen fit to mention us.”

“I apologize,” Reigen said, “I don’t think I brought enough food for guests.”

“We won’t be here long.” Suzuki snapped his fingers. At the signal the remaining Ultimate 5 dived into the water. When they emerged, it was with the remaining gold bars.

Reigen’s expression was unreadable. “That’s a nice little nest egg,” he said, tone flat. “They should go back in the water.”

The Chairman gave the human a hard stare. He wasn’t expecting his gift to be rejected so soundly. “Don’t you want them?” Suzuki asked.

“The human world is complicated,” Reigen explained. “There’s salvage laws, sovereignty, rules I probably don’t even know about.” He ran a hand through his hair. “Look, I can take one more now just to make sure that Serizawa and I can make it through our first few years here, but I won’t touch the others. Not unless we really need to. I won’t risk Serizawa being discovered over some sunken treasure.”

They all knew what discovery could mean: separation, experimentation, death. Reigen had a right to be paranoid.

“It seems,” Suzuki said after a few tense moments, “that you have earned your happy ending. We’ll do as you wish.” He turned his attention back to Serizawa. “You can stay with us until your new home is built, then you will be in your human’s care.”

It was the best outcome Serizawa could expect. “Thank you.”

Ever the salesman, Reigen picked up on the social cue. “Thank you.” He bowed to Suzuki, “Thank you for allowing me to take care of Katsuya.”

“We’ll be back,” Suzuki said, “when your home is finished.” The Ultimate 5 went down into the cove’s waters, to hide the precious treasure from human reach. It was Serizawa’s dowry, his future. Only he would have control over it as he saw fit.

That suited the merman and his human just fine.

Over the decades, there were many rumors about the man who lived in the house that met the sea. Reigen Arataka was charming, fascinating, sociable, yet no one had ever been to his home. They saw the photographs he had on his phone, but he never invited another soul over.

Despite this, he never seemed lonely.

He worked at multiple jobs throughout the years, restaurant ventures, internet startups and the like, always folding when it no longer tickled his fancy.

Yet, he seemed to never lack for money.

No matter how many pretty faces battered their eyes or inquisitive old men snooped, no one could pry his secrets from him. It never bothered Reigen and thus it never bothered the townsfolk. Much.

He kept to himself; made few but lasting friends and was generally a helpful soul.

It was not until he was old and gray, when the nurses came to assist his ailing mind that new stories circulated. Stories of a love that breached the divide between earth and sea, stories of a dedication across the decades, of an adoration that could survive even death. That late at night, the very sea seemed to weep for a lost love. Some suspected that these were the idle fancies of bored nurses, but others wondered if there was more to it.

Only Reigen Arataka knew the truth and he never told.

He took his secrets to the grave.