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Curiosity and Inevitability

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Kacchan smelled really good that day. Izuku couldn’t help but take an extra deep breath every time he looked up from his notes at the teacher at the front of the room. Katsuki was sitting in front of him, as always, and was completely focused on the lesson. But Izuku found the invisible scent trickling off the blond to be one of the most distracting things he had ever had to deal with in the classroom since they got into UA. Yet the shorter boy toughed it out, getting through each class until the bell for lunch rang. As everyone began to head for the cafeteria, he took the opportunity to ask quietly, using the noisiness of their classmates to drown him and Katsuki out.

“Kacchan, you smell really good.”

The blond narrowed his eyes with a huff. “Is that all you’re bothering me for?”

“I was just wondering…are you in heat?”

Katsuki clicked his tongue in distaste. “Shit! It’s that noticeable?”

Immediately Izuku waved his hands defensively in front of him. “Uh, n-no! I mean, I can always smell when you’re in heat, anyway. I can smell when Uraraka and Todoroki are too! It’s not a big deal! Just…you know… It’s kinda strong today is all…”

The blond rubbed at his neck, against the slightly-swollen scent glands. The motion did little but send out yet another wave of the sticky sweet scent that had clung to Katsuki since he had gotten his quirk. Izuku narrowly managed to not wrinkle his nose at the assault.

“Got up late. Couldn’t get a shower this morning. I’ll go to the locker room after I eat and grab one.” The blond explained. “Now is that all, nerd?”

The shorter boy gave him a shy little nod and Katsuki stormed out of the room with his friends who were waiting for him by the door. Izuku sighed and followed. He took a deep breath of the relatively-clean air of the hallway before heading for the stairs where he could see Ochako, Tenya, and Shouto walking slowly for him to catch up with.

True to his word, Katsuki was much less smelly when they got back to class after lunch. His hair was still a little damp, so it was obvious he had gotten the shower. Izuku couldn’t help but breathe a sigh of relief. Like any alpha who was at least minimally respectable he could control himself around an omega in heat, he wasn’t Minoru (who for the record was a beta), but being able to focus on classwork was always harder if someone’s scent was too strong. Or in Katsuki’s case, strong and near.

That said, though, curiosity had begun to creep up on Izuku. It often did whenever one of his friends was in heat, but of course he never voiced his curiosity. Even if his question would be entirely innocent and educational in their purpose, it was still inappropriate! So instead he opened a second notebook on his desk and scribbled down questions he had when he thought of them so as to get them out of his head the best that he could.


In the afternoon Izuku and Katsuki had scheduled a sparring session. It wasn’t uncommon for the two of them to spend upwards of an hour going at each other. Their brawls were vicious, as neither of them held back save for not being allowed to destroy school property, and they often ended when one or both (usually both) of them were on the ground panting and unable to move anymore. Large bruises and scrapes would litter their bodies for days afterward.

That afternoon when Izuku caught up to his friend outside, he already knew that something was up. Usually they would stretch first, and if somebody arrived at their meeting spot early they would go ahead and do so. Katsuki wasn’t stretching. He was just sitting on the grass looking at his phone.


The blond glanced up at him before returning his attention to his phone. He was texting somebody. “I’m canceling today.”

Izuku frowned and opted to sit beside him. “What’s wrong?”

“Feel shitty, that’s all.” He stated.

“Is it because of your heat?”

He nodded. A moment later and he finished his text and stuffed his phone into his pocket. “It’s a nasty one this time. Don’t feel like doing fucking anything.”

They’d sparred together while Katsuki had been in heat several times before. And if it weren’t for his scent giving away his condition, Izuku would have never known. Heat or no, Kacchan was always Kacchan. For the blond to cancel just because of that meant he really wasn’t feeling well.

“Wouldn’t you rather be inside then? Like, in your room or something?”

The blond grunted and laid back on the grass, closing his eyes with a sigh. “Room’s too fucking hot, even with the AC on or the window open it feels too stuffy. Breeze feels nice…”

Izuku leaned back on his palms. He stared up at the sky. It was rare for him to get to have a quiet moment alone with Katsuki. And even rarer to have one where the blond was being…calm. Tranquil, even. Come to think of it, he hadn’t really been fussy at all that day. Thinking about that for some reason made Izuku recall all the questions he had written down after lunch. Questions that he was dying to know the answers to, but unwilling to just ask because of their nature.

Fortunately for him, Katsuki was getting better at reading him like a book.

“The fuck are you contemplating your navel for?”

“Huh?” Izuku looked down at his friend, who was glaring at him from the grass below. “I was looking at the clouds though?”

“It’s a figure of speech, dumbass. What’ve you got rattling around in your head? Just speak up already before you start muttering!”

There was the aggression Izuku was more familiar with. It made him smile. “Well…since you’re asking… I was just wondering what it’s…you know…”

“What it’s like to be in heat?” the blond asked. The shorter boy nodded. “Of course you wanna know, you freak.” Izuku flinched at the harassing, but Katsuki just sighed. “It’s annoying. That stupid myth that men think about sex every seven seconds? Imagine if that were accurate.”

The shorter boy couldn’t help but cringe. “That…sounds a lot like what it’s like to be in rut.” He stated sympathetically.

“What else?”


“You looked like you had more you wanted to ask me.”

Izuku flushed a little in surprise. “O-OH! Well, uh, if you don’t mind… Um…is it true that you have to bathe more often?”

“Shouldn’t you know that? You’re always watching me like a creep.”

“I don’t watch you that much!”

Katsuki huffed like he didn’t believe him. Izuku couldn’t blame him. He didn’t believe himself either, even if it was true that he didn’t know the bathing habits of omegas in heat. He knew that some omegas, such as Denki and Yuga, didn’t care and stuck with what they usually did. But it was “common knowledge” that omegas bathed more frequently when in heat as a courtesy to others. Alphas were much the same way. Though it hadn’t been uncommon in middle school for newly-presenting alpha boys to not bathe at all just to childishly throw their obnoxious scent around. They were often given detention for it and made to shower in the locker rooms, since it was intentionally causing a distraction.

“Twice a day is the recommended amount. Once in the evening because of how much we sweat in a day, and once in the morning because we sweat a lot at night too. It’s annoying as shit but not the worst thing in the world. Don’t you do that, too?”

Izuku nodded. “So um… Does it…hurt? Or anything?”

The blond shrugged. “Sometimes makes my stomach churn, or I just feel lethargic. Sometimes my joints ache or my muscles are sore for no reason... But really it’s the other shit like intrusive thoughts that’re most annoying and I gotta deal with.”

The shorter boy was silent for a long moment, debating with himself whether he should ask his next question. His cheeks turned pink and he couldn’t look at his friend when he finally decided that he may as well pose it. After all, when would he get another chance to ask?

“Is it… That is… Does it help to…you know…?” He made a jerking motion in the air and his cheeks burned brighter.

Katsuki actually barked a laugh at that. “Sometimes.”


“Depends on my body’s fuckin’ mood! Sometimes I can just ignore this shit, sometimes I gotta cum three times just to get to sleep. I don’t fuckin’ know, and I don’t think my heats do either!”

“Three times?!” If it weren’t for the fact that Izuku’s mind immediately went to imagining how desperate his childhood friend must be during those occasions, stroking himself and whining with frustration and staining his sheets yet again, he would be impressed that he had the stamina to do that ever. Let alone often enough that he made mention of it.

“Oi! Stupid Deku, what the fuck are you thinking about suddenly!?”

The shorter boy physically had to shake his head to clear the thoughts away. “S-Sorry! That’s just, you know, impressive.”

The blond narrowed his eyes at him again and finally sat up. “What about you? Ruts aren’t pleasant either, or so Kirishima and Ashido have told me.”

“Ah, well…it’s… Similar? Ah but, m-masturbating doesn’t…it doesn’t help much…at all. Actually it’s pretty different, I guess.” Katsuki raised an eyebrow, prompting Izuku to elaborate. “It’s… Less that we want to, y’know, c-cum. And more like…more like we actually want to…to have sex with somebody. Our knots rarely pop when we just…use or hands. Or at least, mine doesn’t.” he scratched the back of his head shyly. “Plus biting a pillow isn’t very satisfying.”

“So get yourself a sex doll or something.”

“KACCHAN! First of all those’re expensive! Second of all, that’s just weird!”

The blond shrugged. “Some other sex toy, then. There’s gotta be some synthetic asshole and an omega-scented lube or two on the market. After all, there’s knotted dildos.”

He was afraid to ask, but Izuku did anyway. “Let me guess; you know that because you’ve looked.”

Katsuki smirked. “I own one.”


“Would you stop shouting my name like that?! And is it really that surprising? I can guarantee that every damn omega in our dorm either owns at least one, or wants to own one. Shit’s useful!”

“D-Does it really feel that good?”

Almost immediately Katsuki’s eyes glazed over. Just a little. “Fuck yeah…” he nearly purred. “I’ve tried using a regular dildo. Shit was fine, did the job. Just kinda left me feeling wanting. The knot really helps.” Izuku caught another whiff of the blond’s burnt caramel scent. There was no denying that a sudden spike of arousal had been the cause for its release. It made him shudder and involuntarily open his mouth a fraction. There was a pause and the taller boy blinked, shook his head in agitation, and got to his feet. “You done asking me shit?”

“Ah! Uh, yeah. I think I’m good.” Izuku replied, getting to his feet as well. “Thanks for answering.”

“Whatever. Beats listening to your incomprehensible muttering the middle of class.”

That wasn’t surprising to hear. Izuku was just glad that he had described it as “incomprehensible”, which meant that nobody actually knew what he had been muttering about. It would have been embarrassing if they knew. The two brushed the bits of dry grass off of themselves and then headed back to the dorm together. Without another word, Katsuki stalked on up to his room.

For his part, Izuku went about his usual post-sparring evening. Homework, chatting with friends, dinner, a shower. Not necessarily in that order. Everything was normal. Except for the fact that nearly every time he had more than five seconds to just sit and think, the image of Katsuki fucking himself on a synthetic knot tried to worm it’s way into the forefront of his mind. It made him squirm. The look he saw earlier on his friend’s face combined with the burst of scent caused by arousal…there was little doubt in Izuku’s mind that the blond was upstairs in his room doing things to himself. And for some reason that was doing things to Izuku.


The curly haired teen woke up in his bed feeling like his entire body was on fire. He had kicked off his sheets in his sleep and had evidently writhed about enough that his shorts had ridden up to the tops of his thighs and his shirt was up near his collarbones, trying to expose as much of his heated skin to the air as possible in a vain attempt to cool down. His skin was damp with sweat, and a heady smell permeated the air. Everything came together into a sensation that Izuku had come to know all too well; he had gone into rut while he slept.

He rolled onto his side and picked up his phone from his nightstand. He was momentarily blinded by the screen coming on and he raced to dim it. He stared bleary-eyed at the time that was displayed. He groaned. It wasn’t quite three-thirty in the morning. He turned the screen off and placed his phone back down before rolling onto his stomach. His rut was still in its early stages, so the feeling of horniness hadn’t quite hit him yet. Not that it ever helped him much anyway, but jerking off wasn’t going to relax him any at that point. Instead he closed his eyes and hoped that he could get a few more hours of sleep in, even if they ended up being restless.

Sure enough, the remainder of Izuku’s rest was broken and wrought with fits of being overheated. By the time his alarm went off he was feeling groggy and wanted nothing more than to douse himself in a nice cold shower. Normally he was supposed to go running in the mornings along with most of his classmates but he decided against it. Instead he gathered up his uniform and shower supplies and made his way downstairs to the communal baths. He was pleased but not surprised to find them empty. Hardly anybody ever bathed that early in the morning and he really just wanted to rid himself of his rut stink without bothering anybody else.

He had just finished stripping off the last of his nightclothes when the bathroom door opened. On instinct Izuku turned to see who had come in. Despite knowing full well that the blond would be showering that morning too, it still took him by surprise to see Katsuki entering.

“K-Kacchan!” Izuku shouted, suddenly feeling hyper-aware of himself, the other, and their surroundings even though they had shared the communal showers and baths for two years and had thus been naked around each other plenty.

The blond momentarily blinked in surprise, his nostrils flaring for a second before he walked passed the shorter boy and set his belongings down. “You’re in rut.” It wasn’t a question, and he stated it as if he was commenting on the weather.

Izuku’s cheeks burned and he grabbed his shower supplies. “Y-Yeah…”

Katsuki clicked his tongue and stripped himself of his tank top. Izuku’s eyes couldn’t help but follow the motion, taking in every inch of skin that became exposed in the process.

“It’s a bit early for you, isn’t it? You’re normally in rut around the middle of the month.”

The shorter boy stared at him, dumbfounded. “You know that?”

The blond began to lose his shorts and underwear. “I know when every goddamn alpha in the class is going to be at their most obnoxious. I’m surprised your stalker ass hasn’t learned every single person’s cycles back in our first year.” He tossed the last of his clothing aside and turned a glare over at the other. “Or have you?”

Izuku’s cheeks flared with color again. “J-Just my friends’…”

“That’s easily half the class.”

The shorter boy avoided eye contact. “Okay, so I know everyone’s.”

Katsuki smirked, clearly chalking that up as a small victory on his part. “Well don’t just stand there cowering like a dumbass. Get in the damn shower already! You reek!”

Izuku yelped as the blond grabbed him by the shoulder and began to shove him in the direction of the showers. He stumbled to keep up with his friend’s pushing and was quickly manhandled into an open stall. He heard the curtain behind him slide shut and a moment later the stall’s next to him closed as well. The water next to him turned on and he breathed a sigh. Izuku hung his towel over the curtain rod and turned his own shower on.

The water was blissfully cold on his heated skin. If he had the time, Izuku wanted to stand under it until he no longer felt like he was going to burn up just by existing. Instead he dutifully went about scrubbing the sweat and stink from his body. Over the sound of water he could occasionally hear the echoes of Katsuki doing the same just a few feet from him, separated only by the partition of their stalls. It brought a smile to his face knowing that he wasn’t alone in that moment in the inconvenience that was dealing with having a secondary sex. He wondered if Kacchan felt the same. Probably not, he supposed. Kacchan wasn’t exactly one for sappy stuff like that.

“You’re muttering again, Deku!”


There were a few seconds of silence before the blond spoke again, this time not shouting and only loud enough for the other to hear him. “Were there any other questions you wanted to ask me yesterday?”

Izuku jumped a little. He hadn’t thought about that all morning. He bit his lip and wracked his brain. He was sure that he had written down more things but off the top of his head he was having trouble recalling any of them. He shook his head even though the other couldn’t see the motion.

“I can’t think of any right now.”

Katsuki clicked his tongue. “Meaning there are.” He mumbled. Then, louder again, “Then answer me one; who in our class smells the best?”

“WHAT?!” Izuku’s face had never gone so red so quickly, and his shrill outcry echoed and rang throughout the tiled bathroom.

“Don’t shriek like that! You’re making my ears hurt!”

“Why would you ask me something like that?!”

“Because I happen to know you’re a damn pervert stalker, so obviously you’ve got a preference!”

Izuku gave up on washing himself in order to argue. “I am not a pervert or a stalker! And even if I do have a preference, why do I have to tell you something like that?”

“I answered plenty of your stupid questions yesterday.”

“And I answered some for you, too! As far as I’m concerned, we’re even! And no matter if we weren’t you can’t just ask people that, Kacchan!”

The blond huffed. “Whatever. Finish your damn shower.”

Izuku did just that. He hurriedly finished cleaning himself up and left the shower. Katsuki was still in his by the time he had finished putting on his uniform. As per usual he fumbled with his tie, trying for the umpteenth time to get it right. Even in his third year he still hadn’t learned. Then a thought occurred to him. He glanced over at the occupied stall before cautiously approaching it.

“Kacchan, would you do this for me?”

The water turned off and the blond yanked his towel from the curtain rod. A moment later and he opened the stall and stepped out, towel tied around his slim waist. Izuku fought to keep his eyes trained on his friend’s face and not on all the little droplets of water that littered and rolled down his muscled body.

“Your tie?” Katsuki asked, raising an eyebrow at the strip of cloth hung around the shorter boy’s neck. Izuku nodded.

The blond sighed and took a step closer, reaching out and taking the ends of the tie in his hands. For some reason, Izuku found himself holding his breath while Katsuki (amazingly carefully) did up the last piece of his uniform for him. Being so close to the naked blond, Izuku lost his previous battle and his eyes dropped to where his friend’s meaty pecs sat almost right in front of him. He heard Katsuki inhale deeply just a second before he stepped back again. When Izuku glanced down at himself he was happy to find his tie done up properly. He cast his friend a wide grin.

“Even though you never wear yours, you’re good at doing this. Thank you, Kacchan!”

“We’re third years, Deku. You should know how to do this by now!”

The blond stalked passed him and into the front of the bathroom. Izuku followed after him and hung around only long enough to gather his belongings.

“I’ll see you in class then.”

Katsuki merely waved at him and the curly haired teen took that as his cue to leave. As soon as the door closed behind him, Izuku breathed a deep sigh.

“Stupid Kacchan…” he whispered before making his way back towards the elevators so he could put his stuff back up in his room. “Asking me something like that all of a sudden. I think his heat’s getting to him. It does seem to be a bad one this time around.” He fiddled with the end of his tie before slowly bringing it up to his nose. The scent on it was faint, almost unnoticeable. Had he not been searching for it he probably would not have found it. Burnt caramel. “He really does smell good though…”


Despite his friend having showered that morning, Izuku found himself more distracted than the day before by Katsuki’s scent. Sitting behind him, something like a mere two feet between them, he could smell the other more distinctly than ever. He spent a good while wondering if they had ever had their heat and rut at the same time and could only come to the conclusion that they had not. It explained a lot. The class was lucky in that most everyone’s cycles were off from each other, and the one time he and Ochako had been unfortunate enough to sync up they had had to keep about six feet away from one another because they had been too smelly for each other. Tenya and Shouto had fortunately made good buffers during that time, standing strategically between them whenever they would hang out together.

But he didn’t have that luxury with Katsuki. While they had mutual friends, it wasn’t like their friend groups intermingled much. And if Izuku was ever alone with Katsuki it was always just that: alone with him. There was no buffer readily available for them. And this was only compounded by the fact that they sat so close together in class.

So Izuku sat there, barely half-focused on every lesson as the hours ticked by. Every time his mind wandered, which was frequently, he found himself trying to inhale the blond’s scent just a little more deeply. He kept his senses enough to not do something dumb like lean forward and plant his face in his friend’s neck, but that didn’t mean the thought didn’t cross his mind a number of times.

What would it be like to press his nose right up against the other’s scent gland? To be right there, at the source. The scent of burnt caramel, sweet and sticky and cloying, would infect his sinuses and linger for days after. He wondered if he would taste the way he smelled. If he were to peek his tongue out from between his lips while buried in his neck and lightly skim across the scent gland, would it be sweet? Wait, doesn’t nitroglycerin not really have a distinct taste? So then perhaps it would be salty like normal sweat. Oh but sweet and salty together wouldn’t be a bad taste either. He could lavish those swollen glands with his tongue, becoming intimately familiar with smell and taste intermingling in his olfactory senses and then…

Izuku shook his head in order to clear it and nearly bit his tongue in doing so. Since when had he been licking his fangs?! And furthermore, since when had his mouth been hanging open!? He clamped it shut, his teeth clicking in the process, and refocused his attention on the chalkboard at the front of the room. He had to concentrate! This was no time to be having weird fantasies about his childhood friend!


He had been fantasizing about his childhood friend!

Oh no. Oh no! Oh God that had to be crossing some kind of line, right?! What the heck!? Yeah sure he was an alpha in rut and his friend was an omega in heat, but even when he and Uraraka had been synced he’d never lost his head like he just had. Was it because of their proximity?! That had to be it, right? There was no way it was anything else. Nuh-uh. None. Couldn’t be.

It especially couldn’t be that Izuku had always thought that Kacchan smelled the best out of anyone he had ever met.


The bell rang. It was lunch time. Izuku blinked and realized that he hadn’t written down any notes from their last class at all. With a groan he resigned himself to asking to copy his friends’ once they were back at the dorms.

“Oi, Deku!”

He glanced up and was surprised to find the blond looming over him. Okay, maybe not looming. Just standing beside his desk. But thanks to Izuku’s dumb perverted rut-brain he couldn’t help but feel guilty and that guilt made him feel a thousand percent tinier and Katsuki appear a thousand percent more intimidating than the blond was actually being. Wait was it just him or was Kacchan looking a little…flustered?


“Here.” A notebook was dropped on his desk. “Copy ‘em over lunch and give it back at the beginning of next class.”

Without another word, Katsuki turned on his heel and left. Izuku stared after him for a second before looking down at the notebook. He picked it up and flipped it open. Sure enough, each page was filled with the blond’s neat and organized scribbling of all the things they had been learning recently. It didn’t take him long to flip to the pages with that day’s notes and Izuku shut it before thanking the gods for having mercy on him.

And if he discreetly brought the notebook up to his nose while gathering the rest of what he’d need to copy the notes while he ate his lunch, well that was just more guilt to pile onto the heaps he had already accumulated that day.


The third day was the worst. It wasn’t unusual for the third or fourth day, whichever was the last one of Katsuki’s heat, to be the one where the blond smelled the most and this time was no exception. Izuku couldn’t help but avoid the other as much as humanly possible in order to stave off as many quite-frankly-lewd thoughts as he could. The fact that they sat so close together in class however really was not helping him in his efforts. More than once between classes the shorter boy had had to leave the room. Not to seek release, but rather just to breathe air that wasn’t tainted with the cloying smell of caramel.

Katsuki himself seemed to need to leave the classroom a lot, too. But he always stalked off somewhere away from Izuku. That was until the short span of time they had between their last classes. Instead of going off somewhere else, the blond approached the shorter boy in the hall.

“Deku! Come up to my room tonight. I wanna talk to you about something.”

Izuku nearly jumped out of his skin at the proposition. To be invited to the other’s room was rare as was. To be invited while they were in the midst of their cycles and already having as much trouble as they evidently were with each other’s scents… Izuku shook aside the new onslaught of intrusive thoughts. When he met Katsuki’s eyes again, he couldn’t help but notice the way the blond had subconsciously taken a deep breath. Whether he noticed it or would admit it, the omega was definitely being affected by the scent of arousal that had to have been wafting off of Izuku.

“Couldn’t we have talked during lunch?”

“No. My room, eight o’ clock. God it?”

“Y-Yeah! Got it.”

The blond blew out a short breath through his nose before turning on his heel and heading for the bathrooms for what was probably the sixth time that day. Izuku lingered another minute or two out in the hallway before taking a deep breath himself and going back into the classroom. Katsuki returned not thirty seconds before their last teacher arrived.


To say that Izuku was nervous while he stood in front of Katsuki’s door was putting it mildly. He’d been inside dozens of times, but never while in rut or while the blond had been in heat. He had no idea how much it was going to drive him mad to be absolutely surrounded by his friend’s scent within the confines of what was effectively his nest. Taking a deep breath he raised a shaking hand and rapped lightly on the door.

Katsuki opened it and, sure enough, the concentrated scent of the omega’s heat immediately burst and rolled fourth through the crack. Izuku couldn’t help it, he had to cover his nose and mouth immediately.

“H-Hi Kacchan.”

The blond narrowed his eyes at him. “Took you long enough. Get in here.” He took a step back to let the other in. Izuku inhaled again, this time trying to spare himself from the smell of the room for as long as he could, and stepped inside.

Immediately he noticed that Katsuki’s bed was unmade; a rarity for the blond. While it was relatively clean the trash bin he usually kept in the corner was right beside the bed and stuffed full of snack packaging and tissues. But what was most troubling of all was what sat on the bedside table. In full view, as if Izuku’s childhood friend had absolutely no shame, was a knotted dildo.

The curly haired teen had little time to do more than squeak and go red at the sight before he was suddenly shoved up against the door. Katsuki was in front of him now, blocking his view and standing dangerously close. The blond’s mouth was open and he was breathing deeply. Up close and no longer flustered by the first whiff of the room Izuku could see that Katsuki was already sweaty and his heat-scent was more cloying than ever.

“Kacchan, are you-“

“I’m going to ask you this again, Deku. Who smells the best in the class?” the blond murmured, his hot breath ghosting over Izuku’s face.

The shorter boy shuddered. Already he was feeling himself trying to breathe in that scent more deeply. And this time, for whatever reason, allowed himself to. “Kacchan… Why are you asking me?”

“Just answer the question.”

He swallowed thickly, tasting the scent all down his throat. “I… I like Kacchan’s the most. Of anybody’s.”

Katsuki smirked and leaned in closer. His nose pressed up against his neck right beside his scent gland. “Of course you do, nerd.” The omega breathed.


“Don’t think I haven’t been able to smell the way you’ve been turned on ever since the other day. When we were talking instead of beating the shit out of each other. Is that why you went into rut early? Couldn’t stop thinking about me getting fucked?”

Izuku shivered. Whether it was true that that’s what had triggered it, he couldn’t deny the rest of it. “Kacchan’s… Kacchan’s always smelled really good.” He repeated.

A tongue pressed beneath his ear and dragged down his neck to his scent gland. Katsuki absolutely groaned into his neck and closed the space between them, pressing their bodies together against the door. There was no way Izuku couldn’t feel the hard-on pressed against his hip. Just as there was no way that Katsuki couldn’t feel Izuku’s erection on his thigh.

“Stupid fucking nerd. Why do you gotta smell so damn edible? I wanna fucking eat you right now.”

Izuku couldn’t help but laugh weakly. “I don’t know whether I should feel threatened or excited.”

“Seem pretty excited to me.” Katsuki replied, pressing his nose against the scent gland and gently rocking his hips forward.

“You’re one to talk.”

“Shut the fuck up.”

Before Izuku could react there were lips upon his. Katsuki kissed him like he did anything else: brashly and with fervor. It was all Izuku could do to wrap his arms around the blond’s shoulders and hang on. Try as he might, Izuku was just barely able to keep up with the messy kisses and rough bites that were assaulting him. Somehow somewhere along the line the omega had managed to coax his lips apart and was doing his level best to swallow his tongue. Or at least, that’s what it felt like. All the while the blond continued to grind their erections against each other.

The alpha was certain he had been near to passing out before he was finally allowed to breathe again. His head dropped forward onto the other’s shoulder and at long last it was his turn to take in the other’s scent right from the source. He was aware that he was panting and making some weird sounds, but Izuku was too focused on trying to fuse his face to the other’s scent gland to care. Try as he might the shorter boy felt like he just couldn’t be close enough to it. He tried licking it, the taste salty despite the smell being so sweet. It was thick and overpowering, and so very not enough. He moaned.

“Kacchan…” Izuku whimpered.

Then all at once everything went away. The smell, the taste, Katsuki’s warmth, the erection frantically rubbing against his hip, everything. Dazed, Izuku nearly stumbled forward and he raised his head to see the blond had stepped away in order to sit on the edge of his bed. Without being told to, Izuku followed him and came to stand between his legs.

“Suck me off, Deku.” The omega purred.

Izuku was on his knees in a flash. Katsuki’s sweatpants came off easily, and it was only marginally surprising to find that the omega hadn’t been wearing underwear. His erection was red and throbbing, precum spilling freely from the tip. But there was more to it than that. The curly dark blond hairs surrounding it were matted with cum, and suddenly the omega’s sweaty state when he had answered the door made sense. Katsuki had just finished getting off at least once by the time Izuku had knocked. He hadn’t been late, which could only mean that the blond knew he was going to need to cum many times that night.

“The fuck’re you waiting for, shitnerd?!” Katsuki growled.

“Right! Sorry.” Izuku immediately leaned in and pressed his tongue to the underside.

He’d never had any kind of sex, but he had seen his fair share of porn. Although he really couldn’t think in that moment he still tried to recall everything he had ever seen. He brought his tongue up to the tip, lapping up the salty and bitter precum along the way. He held Katsuki’s length by the base while he pressed and swirled his tongue around the head. Above him the blond groaned and buried his fingers into Izuku’s hair, gripping green curls tightly. Izuku closed his lips around the head and sucked a few times. The omega gasped.

Then Izuku began to bob his head. Each time he went in he took a little more of the other into his mouth, sucking the entire time. He wanted to use his tongue more but didn’t have the experience for that sort of coordination. So instead he focused on what he could do. And with every inch he took Katsuki seemed to lose himself more and more, the blond panting and moaning. By the time Izuku was able to bury his nose into the filthy and pungent hairs at the base of the omega’s dick Katsuki was lying completely on his back and making such delicious noises.

Izuku swallowed around him a few times, moaning himself at the heady scent and taste that was assaulting his senses. It caused Katsuki to weakly buck up beneath him. The alpha dutifully returned to his task. He drew off the other with a slurp and a wet pop before diving back in. He kept at it, the pace brutal on his throat but worth it for the way the omega whined with pleasure and need. Such a feral, desperate sound. The alpha had never heard such a sound in his life and it was easily as addicting as his friend’s scent and now taste.

“Deku…!” the omega keened. “I-I’m… I’m… C…cum…”

The shorter boy groaned and took the other’s dick as deep into his throat as he could and was rewarded by the other releasing directly down it. Izuku swallowed everything down and came off slowly, lips still sealed around him so as to clean off any last drops. He wasn’t surprised at all to see Katsuki gasping for breath on the bed, delirious from his climax.

He allowed the other a few moments to recuperate before he spoke.

“Anything else you want from me, Kacchan?”

The blond’s limp dick gave a weak twitch and Katsuki raised his head to look him in the eye. “Yeah. Fuck me.”

That made Izuku whine. But he didn’t move from his spot on the floor. “Are you sure, Kacchan?”

“Positive. Get up here and pound my ass into this mattress. And I swear if you don’t shake the bed enough to put a hole in the wall, I’ll kill you!”

Izuku didn’t need to be told a third time. He got to his feet and collected his childhood friend into his arms in order to move him further up the bed. Katsuki wrapped his arms and legs around him and brought their mouths together again. He was deposited none-too-gently back on the mattress, Izuku going down with him. In a flash every last piece of their clothing was gone and they ground their naked erections together between their bodies while they kissed.

“Lube?” the shorter boy asked between bites to each other’s lips.

“Beside the dildo.”

Izuku looked and sure enough there was a nearly-empty bottle sitting beside the dildo on the nightstand. He couldn’t help but ask as he pumped some onto his fingers, “When did you buy this?”

“Just before my heat started.”

The bottle wasn’t small, and if that didn’t paint a beautiful picture of two long nights and three equally long mornings filled with desperation and need, Izuku didn’t know what did. The blond’s nostrils flared again.

“Stop thinking about it and fuck me already!” the blond barked.

Without further ado Izuku’s fingers found Katsuki’s backside and plunged inside. The first one went in easily, which wasn’t shocking considering how much the blond had to have been using the dildo in the last 72 hours. What was mildly shocking was how slick he already was. A quick glance at the dildo and Izuku noticed that it had a bit of a sheen to it. So, the omega had used it to get off before Izuku had arrived. With that in mind he went ahead and slid in two more fingers and went to town on the other’s prostate. Katsuki moaned again, back arcing off the bed.

“Fuck yes!” the blond groaned as Izuku continued to finger him, punishing his prostate with every thrust.

“Kacchan’s so beautiful.” Izuku breathed, finding the other’s neck again. He nosed at the scent gland and pressed sloppy, wet kisses everywhere that he could. “Amazing, talented, strong, and so, so beautiful. I’m so lucky to get to see you like this.”

“Quit fucking muttering.” The omega whined. “And get the fuck inside of me.”

Izuku pulled his fingers from his friend’s backside and used what remained of the lube on them to slick up his cock. Katsuki turned his head to watch, eyes raking over the length of it before focusing on the base where the knot hadn’t yet popped. Izuku followed his gaze and shot him a shy little smile.

“It should come soon.” He stated reassuringly. “It usually doesn’t pop until the end.”

“That’s a shame.” Katsuki muttered, dropping his head back onto the bed. “While we’re talking, you want me to get on my hands and knees?”

Izuku flushed despite the fact that they were both naked and about to have sex. “A-Ah! Well, that is, um… About that... K-Kacchan’s butt is nice but… I’d rather uh, you know, look at your front.”

The blond raised an eyebrow. “You’re gonna strain your neck if you try to look at my dick the whole time.”

“Kacchan’s dick is nice too, but that’s not what I meant…” the shorter boy smiled sheepishly and lowered his eyes from his friend’s face down to his chest. It was Katsuki’s turn to look down at where the other was gazing. “I like Kacchan’s tiddies most of all.”

The blond flushed and growled at Izuku. “Fucking dumbass perverted nerd!” he shouted, grabbing the back of Izuku’s head with one hand and forcing it down between his pecs. The shorter boy couldn’t help but giggle and proceed to motorboat his friend. “You’re not helping your case!”

Izuku hummed appreciatively before slipping one of the omega’s nipples into his mouth. He sucked gingerly on it, judging Katsuki’s reaction. The blond softly sighed and slipped his eyes closed, so Izuku sucked harder. With his clean hand the alpha began to rub and play with the other bud while his lubed hand grasped the base of his dick and got himself lined up. A part of him wanted to go right on ahead and thrust in given that Katsuki had been so adamant about getting fucked. But he was still too polite to do so.

“I’m going in.”

“Get on with it.”

He knew that was coming. Which was why he snapped his hips forward and plunged in all the way to the hilt in one swift motion. Katsuki nearly shrieked, back arcing again. He was given a moment to adjust (that was actually just Izuku short-circuiting because of how amazing it felt to have Kacchan all around him, clenching down on him so tightly) and he fell back onto the bed panting again.

“Oh fuck… You’re bigger than I thought…” the blond murmured.

“A-Are you okay!?”

“Wonderful~” Katsuki drawled, a hazy and faraway look in his eyes. “Finally found something you’re good for, Deku. Now get moving!”

For all that Izuku wanted to be gentle, he couldn’t help the blistering pace he immediately set. He was too needy. And from the way that Katsuki wrapped his legs tightly around him and began to thrust back after the first few the blond was needy as well. Izuku’s position against the omega’s chest, while nice, wasn’t nearly enough. He pulled himself further up the other’s body until he was back at his neck. Once more he lavished the sweaty and sticky sweet-smelling column with tongue and kisses. This time, however, his instincts pushed for more. He began to nip at the skin, leaving harsh little red spots in his wake.

Katsuki’s hands were in his hair again and he felt the blond doing his best to get at Izuku’s neck as well. Their height difference made it difficult and Izuku nearly bent the other in half to make it work. Neither stopped moving their lower halves against each other, making Izuku thrust deep inside, as they got into their new position. At long last the knot at the base of Izuku’s cock began to swell and bump against Katsuki’s rim with every thrust.

“Put it in me…!” the blond growled against the other.

“Okay…! I will!” Izuku panted back. “I will, Kacchan. I will! Kacchan! Kacchan!”

The shorter boy dissolved into panting the other’s name over and over again, his hips fighting to keep the pace steady. His mouth practically hung open and finally Izuku gave in and sunk his teeth into the meat of Katsuki’s sweat gland. “Holy fuck!” the blond shouted, squeezing all of Izuku’s body tightly with every shred of strength he had. The alpha whimpered at the feeling of the omega’s ass contracting around him and in one final movement shoved the whole of his knot inside the other. The omega keened and released himself between them as Izuku spilled deep inside of him.

All at once their strength gave out on them and both collapsed. Izuku remained laying on top of Katsuki, both panting and gasping for air and coming down from their highs. The shorter boy shifted a little to get more comfortable and felt the mess on their stomachs.

“You… You weren’t kidding…about cumming…three times…” he had to laugh.

“Was fuckin’…four…actually…”

Izuku’s eyes widened and he managed to bring himself to look the other in the face.

“The last day is always the worst.” Katsuki stated.

“Ah, well…that makes sense, I guess.” The alpha bit his lips for a moment before asking, “Do you want me to jerk you off or something?”

“Nah. I think I’m good now.” The blond closed his eyes and sighed. “By the way, I didn’t hear anything break. So I’m going to kill you.”

Izuku giggled and laid his head on the other’s chest. “We still have time to fix that.”

“Nope. Wanted you to do it this time. Gonna kill you.”

The alpha hummed, not believing him in the slightest. A few more minutes passed and finally Izuku sat up and, carefully, retrieved several tissues from the box beside the dildo and lube. He cleaned up their stomachs and Katsuki’s crotch before gently rolling the two of them onto their sides and bringing another tissue to wipe up some lube around the blond’s backside.

“So how long’s your knot stay inflated?” Katsuki finally asked.

“Uh… About an hour?”

The blond clicked his tongue and put an arm around Izuku, pulling him a little closer. “Guess you’re sleeping here, then.”

“If you’ll let me.”

I haven’t got much choice. It’s late and I’m exhausted. Do what you want if you’re still awake later. I don’t really care.” He closed his eyes and settled in.

“Okay, Kacchan. I’ll stay.” Again Izuku pressed his face between the other’s pecs. He didn’t motorboat them again, but he did press a kiss against his sternum with a happy little giggle.

A few minutes passed and Izuku was finally beginning to feel sleepy. He had been tracing mindless patterns into Katsuki’s back and side with his fingertips. The blond didn’t seem to mind, but gave a couple of twitches in certain spots that had the alpha wondering if he was ticklish. He couldn’t recall if he had ever been when they were kids. They weren’t ever in the habit of touching each other much even when they were little and best of friends.

That’s when a thought occurred to him.

“Hey, Kacchan…”

Izuku had been half-expecting for the other to already be asleep, but a few seconds later the omega gave a soft, questioning hum.

“Do you think this was inevitable?”

“The fuck are you talking about, Deku?” Katsuki grumbled, clearly half-asleep and wanting to stay that way or more.

“We’ve known each other since we were babies. And we’ve been through so much together. And we’re an alpha and omega. I was just thinking…it kind of feels like the two of us doing this, having sex, was something that was bound to happen eventually.”

“You’ve been thinking about this shit too much.”

“I actually haven’t! It only just occurred to me.” Izuku went back to tracing his mindless patterns. “I’ll admit… Even though you’ve always smelled really good, I’ve never imagined something like this happening. Not even as a fleeting thought. But now that it has, it just seems like I was an idiot for never thinking it would happen.”

“You are an idiot.” The blond huffed. There was a pause before Katsuki added, in a lower voice, “I dunno about fate or whatever bullshit you’re talking about, but I’ve always been of the mind that if I ever had to be knotted by some annoying alpha, it should at least be the alpha I tolerate most. So stop mumbling and making me reconsider you as being that alpha and let me sleep.”

Izuku giggled. “Okay Kacchan. Good night. And…I love you too.”

“Never said that.” Katsuki muttered and ran a hand through the other’s curls. “But…yeah. Whatever. Good night.”

A while later Izuku was just awake enough to slip his flaccid and deflated cock from Katsuki’s ass. He snatched up another few tissues and finished wiping them both off before finally settling in against the blond to sleep.


The following morning both boys waited until the rest of their class was out on their runs before going downstairs to shower. They both reeked and were covered in each other’s scents. Katsuki followed Izuku into his stall, though, and that time Izuku was careful not to put his knot inside. They didn’t have the time before class for that kind of thing. However he did leave a matching hickey on the other side of the omega’s neck to go with the prominent bite mark that he had already been sporting.

They may have been able to wash off the evidence of who they had done, but there was no way that the blond was going to be able to hide the what. Somehow, neither of them really cared about that part.