Work Header


Work Text:

Maybe it starts one day, unnoticed by the ever changing tide of his days. From school to working part time jobs, Tanjirou doesn't really remember when he has the time to study; much more if it was for rest. There's an uninhibited feeling of warmth whenever he hits the bed — the softness of the mattress enough to sink himself to sleep. But that night led to a different fate. A beat, a pause, then as if suddenly guilty of his dropping grades, Tanjirou decides to stand up for once, get his bag and open his notes.

Or as well as notes could be — he doesn't have much, it's all scrawls and scribbles because he drops his head from exhaustion at class sometimes. But, he can get by. Tanjirou was an honor student sure, but he wasn't the most intelligent nor was he the most organized. His grades are even slipping, but it isn't anything to be alarmed by. At most Nezuko does the cleaning up bit in the house, his room is relatively simple enough that there isn't really much for his room to become cluttered to begin with.

Browsing through his Math notebook, he sees on the third to the last page — in the middle of all the pointless things he's written — a note. It isn't written by him, that's for sure. It's neat and proper, much like his, but there's the different way of writing like it was a very sacrilegious thing to be anything but this. He inspects the page, thinking maybe it was Inosuke or one of his siblings, but the way it's written feels much too distant, much too familiar. Like it's been written by someone who knows him, but they don't, at the same time.

He holds the flimsy paper in his hand. Tanjirou thinks that he should find the culprit first, he searches for clues on the blank page. Other than ∆, nothing of use is left on the note. He brings himself to write something but unprecedentedly stops. What use is it to write on this notebook? He has to find the one who wrote it instead.


How are you? It's been a long time.
- ∆




He asks Inosuke if he knows anyone who goes by the alias of a triangle. Inosuke as usual huffs, it wasn't his thing to remember names but he can associate faces with various different syllables and that's fine. When Monjirou asked him of this triangle guy he doesn't think he's encountered any person with that kind of name.

Triangle, triangle? Why would you name your child Triangle, what bad taste!

"Oh and, Inosuke! If you get a bit of information be sure to tell me okay!" he hears the faint voice of Gonpachirou in the distance and he thinks he should absolutely find this Shiangle person immediately, then Gonpachirou would surely acknowledge him as a rival worthy of his strength.

And in the days that followed, Tanjirou asks more and more people. Inosuke keeps count of the number of competitors he now has and sneers. These ants would definitely be but small fries compared to Inosuke the Great!



He doesn't remember why he hasn't stopped asking people here and there. He goes about asking about a triangle. His classmates are okay with it at first, it's Tanjirou, people tend to accept him for what he is. He's the kind older brother ikemen type, no one would be able to say no. So of course after the initial greeting and the first question, they'd regretfully answer 'No, I don't know anyone who uses that pen name.' But Tanjirou has asked way too much, too many times it feels like he's a broken record. It nags at people now.

Tanjirou just thinks that it has to be someone at school. He only brings his bag at school to and fro even if he does go on different jobs, after all he makes sure to visit his brothers and sisters first before leaving for whatever job he has scheduled just then.

It's tiring, both the routine and fruitless asking. He's not stupid, or at least he isn't as stupid as he likes to think he is. There was no way he would be able to find someone without a name and with just a symbol. It wasn't even written in any fancy script or colored pen, it looked just like any other person's average handwriting and that symbol was as common as any others. Why? Why does he feel like he's missing something important?

He spends his lunches on the rooftop, mostly with Murata and Inosuke. Inosuke steals the food, Murata sulks about the teachers and the school workload, and Tanjirou lets Inosuke eat part of his meals. Usually, that's the case. But it isn't now.

He's thinking, of Nezuko who's in middle school now and his other siblings, of the smell of wind as it passes by holding onto fleeting secrets, and of course, the note. The note is simple and direct enough but Tanjirou doesn't even bother to reply, no not yet, or maybe, he should have — long ago. Yet it stays as his dilemma for the week, it plagues his mind. He can't get it out of his system. The school midterms are coming soon. He doesn't have time to think about this yet he still does. A small voice in the back of his head calls out and tells him to reply, even if it's been a week. Or it'll turn into months, then to years and then— the other side doesn't need to wait that long do they?

He has a pen ready, always, for others or for himself. It's kind of funny how people always forget their pen. He's always been like that, a model student who everyone looks up to and can rely on; except for the earrings.

He doesn't get why he has to hide them, there was no valid reason, not even Tomioka-sensei's malicious gaze or his alarming speed in running. It's trained him actually, makes the delivery for bread easier when he only has a bicycle. Tanjirou gives him his sincere thanks.

He opens the book to the same page as before, the third to the last page of his Math notebook, and written there is a new note. He's dumbfounded, very much so, he decides to just stare. Stupidly.


Stop searching. It's making me feel paranoid.
- ∆


"Oi! Ponjirou! Look, you don't even have a single rice on your bento!"

Oh, Inosuke must have been hungry. He reaches for his bag and takes out some bread, he wasn't feeling hungry anyway. They own a bakery and it might be a small one but it's booming in business so he can take some liberty and sneak a few pieces of bread here and there for him and his friends.

"Have this too!" He smiles, Inosuke should eat a lot since they're both growing after all. Inosuke frowns at him, Murata's laughing on the side.

"Aren't you both just blockheads?" And Murata bursts with laughter.

His lunch ends without him ever writing on the notebook. But he's thought it through, since it's someone who knows he's doing a search then it really did rule out the possibility of it being someone outside of school. Plus they should be here if they could write something now.

He contemplates on it during the last period, Math. Of course he has his notebook open but he isn't listening. It's easy, what's being thought. Just some circles and parts of it and he could easily pass it without much trouble. Then, on a whim, Tanjirou finally decides to write a reply.


Who are you?


He actually expects some sort of magical writing to appear as a reply but the bell rings and there isn't even a single new word on the notebook. He checks just before going home too. There just isn't any.

Just as he's leaving, somewhere he hears a faint sob. But there's no scent of tears.



It isn't a surprise to him when one day he opens his notebook to find another note, or perhaps message; Tanjirou isn't too keen on the phrasing. He thinks it must be hard to keep stealing his notebook at lunch or break just to write something so he tells the other party to just talk to him directly.

There's a looming chill on his back as he writes. Like someone has been waiting for him to write back, it must have been long. For them, to wait like that; but truthfully it's only been a few days. It's not like they could even see what was actually written there immediately. He still feels like a huge burden has been lifted though, both mentally and physically. He continues to study afterwards.

He doesn't pay attention to the sprawl of ink as he closes the notebook.


I can't exactly do that.

- ∆




He doesn't say much after that — or well, write. Nothing much to write nothing much to gain. Yet his curiosity is really getting the best of him, so he asks a question again. This time with much more uncertainty compared to the few times he wrote. This person was shy, that was what he was getting. They weren't trying to act mysterious, just maybe a bit eccentric.


Can you tell me where you are?


And then he feels sleepy, in Math. On the first period on a Monday. He hopes that the teacher doesn't scold him or point him out in front of the class. It's already hard as it is like this. What with managing a bakery and three other jobs, taking care of his siblings, and making sure his grades stay high enough that he gets into a scholarship when he starts at college. It's tough and it feels like its a roundabout way to burn him out. But he couldn't be that kind of person, he was still the eldest son after all.

When he wakes up, it's almost the start of the second period, and then on the open page of the notebook, he sees something written out. It's small and messy, and panicked. Tanjirou feels like he should be reading something he shouldn't, it was meant to be for him, yes but why did it feel like he'd be intruding on someone else's privacy. But he observes the slight smudge of ink on the paper and the obvious dip, obviously from holding the pen there for too long, that it looks rather off than it should be. Still he reads the note, even with how messy it is.


In this everlasting darkness, all I can hear is the sound of your heartbeat.

- ∆




Tanjirou has acknowledged that at the start of his high school, someone has been writing him little messages for him to read at the back of his math notebook and to reply to. He doesn't bother finding out who it is anymore, they don't annoy him per se and up till now he doesn't know a single thing about the other party. But they engage in small talks every day or as much as that could go when a new day pass by before he can get another note.

Lately, he can hear someone sobbing. Quietly, like they're stuck in a lonely place, it isn't a bawl of emotions or pent up anger or grief. It's all just small streams of continuous flowing tears and rain. It doesn't smell like anything, he just hears it in the corner of his room or when he's studying in the classroom. It's a bit creepy but he forgets all that when it sounds so... melancholic. A melody so sad it tells tales of so much suffering and loneliness.

He doesn't understand why this has been happening. And of course he has a sneaking suspicious that the one who always cries by his ear, the one who lets them know of their suffering, it's ∆ isn't it?

He writes another note, they're on the sixth to the last page now — he wonders if they'll get to where his notes are, amidst all the ramblings and getting to know each other, one-sidedly, that is mostly on Tanjirou's side.


Are you the one crying?


And to his surprise, or not, that person doesn't contact him again until much much later. Maybe Tanjirou checks his Math notebook too often on the following days but again, when hasn't he done that?

At least they aren't crying anymore.



Have you eaten yet?
- ∆


It's weird, to see this kind of message when he was sure the other party wouldn't even be able to reply back. What was unusual here is that he was sure that there wasn't a note like this when he checked his notebook minutes ago. He was sure it wasn't there since he checks his notebook too often. Or maybe it really was a trick his eyes made.

But something like this made him really eager to write something back. Tingles form on his skin and he slowly writes out his response.


No, but


Then the pen clatters down to the ground. It fell by itself, but then something is written back on the paper. He doesn't think it's real, something like this. There was ink actually spreading in the form of a ball point writing on his paper. It feels like he's having a dream but he knows he isn't. In the first place he feels like the other person already knows the answer.


- ∆


So Tanjirou goes down to eat the leftovers of miso soup with rice and some bread that hasn't been sold that day. He immediately goes back to his room and he writes a new note. He feels like he could talk to this person but it doesn't feel right to suddenly abandon their original way of conveying their thoughts.

He stays up all night talking or writing and he's about to hit the bed when he suddenly jolts awake. There's an unexpected coldness by his side.

There's a person. Not a person, they're translucent, are they okay?

He fusses. The boy in front of him is holding a pen like he's about to write something but he ultimately gives up. He's floating, Tanjirou realizes and there's tears in his eyes. He looks like faint sunlight. Tanjirou's never met a person who was practically the personification of solitude.

A ghost. It's a ghost. He should be scared, but he isn't. Not when there's a blonde boy with mop-like hair wearing a triangle patterned haori. He's wearing a uniform of sorts and he's crying. Faintly.

He calls out to him, "What's your name?"

And the boy looks at him in response, shock filled eyes and light, and maybe something like recognition. Tanjirou feels warm even when the person — ghost, he reminds himself — envelops him in a cold embrace. He faintly smells the scent of white lilies and the sharpness of winter. He smells a lot like death.

He sits there, patting the back of a ghost, it's weird when there really isn't a body and he's sure that the ghost can't even feel what he was trying to convey.

"Thank you, but I," the boy pauses and takes a shaky breath, "I don't remember."

"Don't worry, I'll help you," and then the boy sobs on his shoulders, it feels as if fate has intertwined them together. A ghost who couldn't remember his own name yet knows who he is. His mind travels back to his first message to him. It's been a long time. Who was he? Tanjirou feels like he should know.

"I," the boy starts, "I don't remember anything. When I woke up, everything was dark. It was so scary! And then I heard your heartbeat."

"It was a gentle familiar sound, so I followed it," he bites his lip, hoping that that's enough explanation. Tanjirou doesn't blame him at all.

"But you said it was a long time?"

"It feels like it has been," the ghost makes another sob, "Who are you?"

"Well, my name is Kamado Tanjirou. And I think we'd get along!" He doesn't ask who he is. Just from looking at his clothes he can already see that this person wasn't from a modern age, he even had a sword. There was no way he died while cosplaying, right?

Tanjirou doesn't realize that he said that out loud.

The boy's laugh starts and it's really contagious.

"Let's get along, Tanjirou."



It's a week before his exams, Tanjirou's been talking to the ghost while reviewing. Surprisingly, they know the topic that Tanjirou's been studying. Even better was that the boy even helped him with it. He feels like the ghost here with him right now was an angel and not a ghost. But he's been told off too many times that he wasn't an angel and he'd retort, not yet!

They talk about the most mundane things, sometimes the boy clutches his head and the memories resurface in the back of his mind. He doesn't tell Tanjirou anything about it, but he looks pained. He must have suffered, and then he looks at Tanjirou with a somber gaze.

He doesn't understand, but he has probably suffered in those lifetimes too. He doesn't ask, doesn't want to make the boy beside him remember all of the cruelest things.

So he lies with him instead, cuddling his arms around as the sobs quiet down and the tears flicker away.



"Tanjirou! I remembered it!"

It's a constant in his life now, for the ghost boy beside him to remember something. He doesn't know how it progresses but slowly the boy regains who he is and what he did before he died. The first fact he learned was that the boy had no parents, he was alone and an orphan that had been picked up by a kind old man. The second was that this person was a scaredy cat even after death. He was the type to always cling onto Tanjirou.

Like he was the one to disappear.

The few things he knew about the boy was that he had lived in the time of the Taisho era. It took a bit of searching for those kind of clothes, he feels like he's seen that haori even before he met the ghost boy. He tries to dig his memories of a triangle patterned yellow haori. Nothing comes up, he sighs.

It's only two more days before his midterms. He's borrowed notes from others, it's really great how kind his classmates are. He probably wouldn't be able to survive the year without a help from here and there. He helps them in return, of course, like tutoring them for a topic — which sometimes ends in disasters — or helping with their projects once he finishes his.

He listens to the ghost hovering over him. Sometimes he also helps in solving one of his math problems or checking his grammar in English. Tanjirou doesn't know why he knows all of this, the triangle boy doesn't know why too. But he helps as much as he can and in return Tanjirou picks up all he can from the boy and writes it down on his notebook. It was their unspoken goal to remember his name and who he was before.

When he sleeps, he weakly registers the smell of sunshine enveloping him.



Too bad the midterms really takes a toll on Tanjirou. He's studying frantically when the last day of preparations come. He doesn't have much time and he even studies when he's on the job, the manager makes him go home early to rest but he's still trying to cram in all the information he can in that thick skull he has.

There's silence when he looks up at his desk. The boy hasn't showed up today. He said that he had something to do and that he'd first leave Tanjirou on his own. It feels empty when he doesn't feel the coldness and pressure of the ghost hanging around in the small room. He doesn't want to admit that he misses the boy's presence. Because as cold as he was, he emitted the light of the sun.

Midterms pass by quickly after that. It's a Saturday the next day so he lets himself fall asleep. It feels warm.



There's blood pooling on his feet. He feels his lungs giving out but he can't give up now. He had Nezuko to protect. He had his friends that were also fighting by his side.

Tomioka-san is already on the verge of collapsing but he's still fighting. He wouldn't be able to stop even if he wants to.

In this Infinity Fortress there were only a few of them still alive. The kasugai crow gives them updates on their comrades once they had split up. Muichirou and Genya were in a critical situation. The crow said they wouldn't be able to survive at this point.

Shinobu-san has also passed away. It was heartbreaking how they couldn't have done anything to help her. To help their comrades, it's a shock how they're still able to keep on fighting.

He's at his limit but he has to continue fighting. Everyone was exhausted and were on the verge of death.

But Muzan is still alive. He's still breathing albeit shallowly, like he's ran out of strength. Tamayo-san, he thinks, nothing would be in vain.

There's a flash and he does his best to block the attack. His sword doesn't break from parrying. But maybe he does.

Zenitsu, he remembers, finally. He was dying. He was dying and now with just a strum of the biwa he's in Muzan's hands. It feels like they're in a never ending loop of despair.

He stabilizes his breathing and charges.



"Tanjirou," Zenitsu whispers to him. It's weak and it feels cold.

"Make sure to be friends with me again next time, okay?" He holds his hands as they face each other. Both of them are losing blood quickly. They'll die won't they? But at least they had defeated Muzan.

Nezuko-chan, sorry. Your brother won't be able to see you as a human again.

He closes his eyes.



He wakes up from a dream he can't remember. He's sweating all over and he hears a sob in the room.


He says like it's the most natural thing. He doesn't even register how it flowed out of his mouth, like he's said it so many times. But there's no one in the room, no familiar coldness in the dark. He touches his own cheeks and realizes that he's the one crying. It flows silently and he doesn't know why.

He forgets the name as quickly as it comes.

"Who—?" More tears drop and then he starts to cry freely. He wants to scream but he knows that his family is still sleeping. It's embarrassing, crying like this. He feels as if he just lost something important, like he's lost the sun.

It doesn't take much longer for him to spring up from his bed to get some fresh air. He rides on a bicycle — the only one they have — and once he gets far enough to the riverbank he let's out a loud scream.

"Where are you!" He shouts to him, he closes his eyes and he feels the air graze his skin. The crack of dawn filling the sky with warm hues.

He was with him just a few days ago! With him by his side. Talking of eating and then helping him with his homework and reviews!

He was there!

He feels his world tilt and he falls by the side of the river. It's damp from the morning dew and the smell of grass and rain is present.

"Who are you?" He whispers, again, hoping that the recipient could hear. His heart is beating fast, mostly from the adrenaline that the impromptu exercise caused. He feels hopeless, and he rolls over to see the sky.

Just to see blond locks hanging from a small face.

"Zenitsu. My name is Zenitsu. It's been, a hundred years, Tanjirou-kun."

He smiles at Tanjirou and then—



And then he disappears.



His life has gone back to normal after that. No more new notes on the back of his Math notebook. Even after he fills it with new questions. He remembers his past too. Being a demon slayer in the Taisho era. He's happy that his family was still alive and intact, even his father was doing well here, since the mark no longer served its original purpose.

He can see the resemblance the past Tomioka-san had with the present one. Their gaze the same freshwater blue with more liveliness to it. Shinobu-san was an upperclassman who they'd meet with whenever there was a needed substitute teacher. Inosuke was the same even after reincarnating. He hasn't seen Makomo or Sabito yet, but they were probably older now that they had a chance to live. The pillars were a complete set too. The important thing was that they were alive and they were living their best lives.

Everyone was here. From his past to the present. Everyone except Zenitsu.

He remembers his quirks and how he used to chase at girls' skirts. That twinkle in his eye when he happened to be praised. He was his support, his friend, his —


He was there with him in his final moments, when he was finally freed from Muzan's grip they delivered an attack, together. Holding on to both their blades, merging into one.

So why? Why wasn't he here with them?

◼ ◻ ◼

It's weird that he woke up from a coma where he felt like he was dreaming. That happened somewhere in the middle of the year or the start. Zenitsu feels like he missed something really important but he doesn't pay it mind because today was a new day of school.

After a month of being bedridden he's finally, finally able to get out! Gramps changed his school even though he insisted that it was fine. It wasn't the school's fault he got hit by lightning and fell into a coma, okay!!

He was going to this Kimetsu Academy when it was already nearing the end of the school year. His anxiety has been making his stomach twist and turn in a way that he wants to vomit. But at the same time he has to keep it in.

He feels like he'll meet his fated one here!! Definitely!!!

He's outside the room and the teacher is telling the class that they'll have a transfer student. He feels his heart is about to burst. Actually can he back out? He's pretty sure he can make a living with his skill in music. He can be a NEET right?

But then the teacher is signalling for him to come in the room and he has no choice but to walk in now. He steps into the room and he feels his anxiety rise up to the top. He's clamping up. His palms are sweating so much. This is bad.

He has to at least make a good impression. He takes a breath and then focuses his ears. He needs to hear the sound of nature. Or anything that isn't the whispering of his classmates.

And then he hears the most gentle sound, he feels like crying. He calms down, that soft gentle heartbeat was something he's heard before, he's sure.

"My name is Agatsuma Zenitsu. Please take care of me!"