This story is also published on ao3, where I update it qucker.

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In the wake of their victory over Fire Hashira, Kokushibō gets wind of a man who possesses the ability to become a partial demon and he thinks that this may be it. His ticket from hell. He decides to use all of the weaknesses of this man to strike a deal.

Genya desperately wants enough power to be able to ask his brother for forgiveness and maybe, just maybe fight by his side in some distant, probably nonexistent future, but on one frosty, bitter night he is unexpectedly given to bite much more than he can chew. It's a slow burn Sanemi Shinazugawa/Genya Shinazugawa with a lot of plot and all the brutality of the 'Demon Slayer's' world (and then some), which means gore and dubcon, but not between Sanemi and Genya.

Their relationship is the comfort part of this story, even if they desperately have to work out some things first. The first couple of chapters are quite light apart from Genya being angsty and finding his footing as a seemingly completely untalented kid among Demon Slayers, but when he is older and left to his own devices, shit happens and the story turns darker from that point forward. The romance is only Genya/Sanemi and Kokushibō is a bastard.

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It wasn't exactly easy, finding a hidden organization, fighting demons most sensible people regarded as a ton of bullshit. He soon understood that he won't be able to find any of the people like his brother. No, when they obviously, desperately didn't want to be found. But he knew one way. If he wasn't able to find the hunter, he had to look for their prey.

First, he tried stupid things, like setting traps with his own blood in abandoned houses, which was completely useless and reckless as fuck. He didn't like other people, for they didn't help him much and called him stupid, when he still was a helpless child, asking people around if they saw any demon killers, so he stopped that for a while.

His brother helped him somewhat financially, but always from a shadow, never visiting, never there, paying for a room and food at a local pub. It ended with him learning far too young how to drink, how to talk to drunk people, and how people were, in general.

And one day he just packed his things and took off. The pub owner took some of his money for keeping his travels a secret from his brother, less than he stole from him here or there on various occasions, so he didn't care much about that one. He was sending the rest to him, whenever he needed it, to points he specified in his letters. Some people said that they never came, seeing him as still being a child they could easily screw over. And they were right because when he tried to break their necks as a thank you, he was still too small, and other adults were always around to stop him. So he had always asked for small amounts, searched for mysterious disappearances in pubs all over the country, and honed his beating skills in bar fights.

Of course, that was another place in which people saw in him only a kid that shouldn't be there, a nuisance or a potential pickpocketer and they often tried to kick him out before he had his chance to eavesdrop in peace or ask any questions. But he never backed up without a fight. That one was a given.

Some people acted nice and tried to give him some food and those he would gladly wipe off of the face of the earth, because he learned, growing up in that very environment that everything had a price, and price for that little bit of kindness was one he wasn't willing to pay. And because of his brother's generosity, which was totally undeserved, he thankfully didn't have to. He had so much to thank him for that it made his stomach hurt.

He didn't do anything for the people that endured that too. He knew that every good intention was a weakness somebody would gladly fuck him over for as a thank you, so he, out of self-preservation, never helped other people that suffered. He suspected that he was not a very good person, a simple opportunist, carrying only for himself, but so were other people, so fuck that.

Finally, finally , the whole city started to buzz with rumors of people disappearing, young boys to be exact, and all he thought was one, big YES. He was at a perfect place, at a perfect time, and a perfect, potential victim to the whole mix! He went outside every night, hoping for action, but all he got was a cold and a runny nose. It was disheartening, to say the least.

One such night he heard screams and he ran towards it with a big grin on his face, only to find a bunch of idiots, mugging some kid. That day he became somebody's accidental hero and even if it wasn't exactly a demon's caliber, he felt oddly light in the corner of his heart, among all that pent-up anger.

But he still ended up having no idea how to look appealing enough for a demon to attack. Maybe he should pay for an advertisement in the local paper. Demons sounded like old assholes that liked to read the news about themselves and then make cutouts.

One evening he dressed kind of neatly and poured all of a perfume sample at a local perfumery on himself in desperation, which earned him a look from the owner, but he promised that he'll buy it when he turns twenty. The guy probably was an old romantic, because he smiled with understanding and mumbled something about the wonderful blooming of first love. He rolled his eyes so hard that he thought they will stay at the back of his skull when he was leaving this shop.

And, which how idiotically it seemed to sound in his own head when he made that plan, it fucking worked.

One moment he was walking on the empty street, the next, someone was putting their paws on his shoulder. Well, he found his demon. The worse part was that there didn't seem to be any hunter at its tail. He felt long fingers on his throat. Instead of trying to try and break out from the clutches, he turned towards it, which earned him a moment of surprise, took out a knife from his sleeve, and struck it right in the throat. 'Die, you motherfucker!' He roared, feeling high on fearful repulsion. It choked and laughed a little.

'My food is dancing on a plate today.' It sang and jumped forward. Ganya managed to step back, but here it was, right after him, claws first and looming over his face. He covered himself with forearm in the last second, before they came down on him. He heard the ripping sound of his sleeve, disintegrating into long pieces before he felt the sting of a cut. And then, in turn, the demon had to step back and cover his face.

'What is that smell ?' He shuddered. 'It's appalling! What a disgusting, nasty, little boy you are! I have no other use for you than to kill you!'

And then, finally, some kid with clothes and a sword a couple of sizes too big came to his rescue. He got rid of the demon in one, swift motion of a wrist and turned to him:

'Why did you risk your life? I observed you, wandering the streets as if you were looking for trouble.'

'Yeah, because that was exactly what I was doing. I wanted to join you!'

'Your fighting skill is almost nonexistent. You were lucky that he regarded you as a kid.' He said in a monotone voice. You are half my age, shrimp , Genya thought angrily. But that made it even worse, didn't it? That scrawny thing could cut him into ribbons before he would lift his finger and it made him painfully aware that he could be too old to start or something. But he will end up a fighter, not as strong as this one maybe, but sure he was good for something?

'Come on, you prick!' The kid only lifted an eyebrow and suddenly, Genya was on the ground.

'Don't be disrespectful to higher ranks. If you really want to join us, here are the coordinates you can try first.' He gave him a small piece of parchment and with that, he was gone.

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He was useless.

A bunch of old, giddy weirdos surrounded him the moment he uttered his full name and in three hours, no less, they discovered that he was good for nothing. No breathing style, no spark of anything, nothing. Nothing, nothing, nothing .

They tried for two more hours at his insistence, full of humiliating desperation and rage, but still with no effect. He spent the next full week trying to find anyone, who would train him anyway, but he didn't have a charm, needed to pull that off. He, again, became a mere nuisance people avoided and he slowly but surely started to despise all that Demon Slayer hierarchy thing the more he ended up at the far bottom of it. At least he learned proper titles like Demon Slayer and Hashira, which apparently meant that you were pretty badass over here.

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Sanemi sat at the headquarters, waiting for the orders, when Shinobu Kocho, the Insect Hashira, appeared at the end of a corridor. And it wouldn't necessarily be something he would even acknowledge, if not for the fact that she then came closer and dropped on the bench right beside him. They both weren't exactly close, Giyū, Water Hashira, acting somewhat as a bridge between them, so he didn't even plan on sending a single 'Hey!' her way. He was irritated at this rapid interest. Fuck, he hoped that she didn't want to ask him for lunch or something. 'I've supervised the list of kids that tried to apply for mentorship this year.'

'Yeah?'

'And I found your surname there.'

He stilled, just a little, but enough for her to see.

'Yeah, and?' He said.

'It's possible that it's someone from your family?'

'I would tell you if you had told me his name.'

'His?' He almost cursed under his nose. 'Genya.'

'Yeah, it rings a bell or two.'

'So I'm happy to tell you that he didn't pass.'

What?

'Yes, I too was surprised at the huge disparity between you two, but it seems that he doesn't possess any talent at all. No one wanted to take him. And they were willing, hearing your name and all that, giddy even, but I asked around and everyone said that he was hopeless.'

'Uhhh, fuck. Thank… God.' And he felt as if some higher power turned its eye on him for a blink of eternity and smiled just for fucking once.

'I thought you would be happy to hear that. And there is even more to it… When I heard all that, I ensured his blood sample would come into my possession. I wanted to check if it had the same components as yours, making it particularly alluring for demons, but tests on demonic objects have shown that not to be the case. It's the exact opposite. Demons seem to really hate the taste of his blood. He would be their last choice for a meal. It's quite amazing. I'm thinking about inviting him to a set of trials to check if I would be able to make a vaccine from his blood, sort of a repeller for demons.'

'Why do you sound like you are asking for my permission? Go to him and don't bother me about that.'

She smiled: 'Thanks.'

That was the best day of that year, no, the last three, no, make it five years. For the first time in his life, he wanted to hug that woman.

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Sanemi's brother was still at the same compound he first unlisted for tests he failed so miserably. She sent Kanao to fetch him, not knowing that it'll become cause of a lifelong misunderstanding. She sincerely assumed that the girl, even mute, would be more understandable and easy to follow for the not-so-very-bright kid than a butterfly. And of course, she armed her with an appropriate letter, explaining the most important points. She didn't take into account that, as it'll quickly and badly turn out, although they were opposites in terms of power and color of hair, the Shinazugawa brothers shared one trait and that was their lack of understanding of the basics of human interaction.

When Kanao came to him and pushed a letter into his hand without any explanation, he was in a state so low that he thought she deemed him unworthy to even open her mouth too.

'What is this shit.' He cursed under his breath but opened the letter. It read:

Dear Genya,

I would like to invite you to my compound for tests on your blood. It seems to possess qualities dissuasive for demons that could potentially help us protect people from their hunger at least to some degree. I hope you can see how useful it can be and would be willing to follow my dear sister, Kanao to the Butterfly Mansion.

With regards,

The Insect Hashira.

Wow, that was amazing and… lame as fuck . That was all he was good for? His blood smelled ? He felt it to be some twisted metaphor for all of his life. He felt oddly self-conscious about it too, as if he went out and discovered that he didn't wash enough or something. It didn't come with good timing either, just when he started working out all the problems coming with entering puberty. In other words, he already felt smelly, slimy, and pretty disgusting with new, different odors coming from his mouth, and also armpits and… other places where he started to grow hairs. He recently decided that the road to becoming an adult was just gross as fuck. And now he discovered that he was exceptionally gross even among other growing guys, who were, mind you, gross enough. That sounded exactly like his damned luck.

He looked at the girl, so girly with all the butterflies, big eyes, and the innocent smell of soap, and he decided that she thought him gross too. She probably knew that he smelled bad for demons. And he grew great hate for her then and there with the passion of somebody highly insecure. Her indifference, which he found extra insulting, didn't leave him with any underlying crush on her, contrary to what usually happened. Instead of seeing a sweet girl with irritating, sure, but also slightly cute superiority, he was so fed up with superiority at this point that he only wanted to puke. No, he saw her from now on as an opponent and everything he wasn't.

Girls like that had sisters that loved them and lived with them and sent them for small errands like 'fetch this smelly guy'. His brother left him and couldn't stand him. Heck, some days he could barely stand his own reflection. With every passing day, he seemed to look more and more like his fucking looser of a father and he cut his hair from his youngest days to cover up their obvious similarities. He tried to look as far as he could from that brutal man, hiding his bestiality from all the outside world behind neatly cut hair and face, elegant clothes, and glasses. People in general were so easily manipulated by appearances that he didn't have any respect for the population as a whole. He didn't even particularly want to save lives. He wanted to have his brother back and help him, and maybe some other people, but in general he was rather disillusioned with humanity. And himself among them.

But the girl still stood there and waited for his reaction. She probably thought him extremely slow with his reading. No matter, he thought angrily and said:

'Fine. I'll come with you.'

She just turned around and started walking, and fast. What a fucking princess.

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Thankfully the road they needed to endure in complete silence wasn't a long one. The lady that went out to greet them was as small and cute as her sister. That was a Hashira, for reals? She smiled at him and said: 'Oh, Genya? I knew from the start. You look an awful lot like your brother.'

'You know my brother?' He asked stupidly but he couldn't help it.

The last time he saw him was at a pub a couple of years ago. He was in his room when he thought that he heard his voice. Doubting that he was right, he went out anyway. And there he was, leaning over the counter, in profile, talking to a bartender.

The one he didn't like, sadly. The guy from the night shift was great and he would tell him what they were talking about. At uneventful nights he amused himself by showing Genya some moves and they spared a lot. He kicked like crazy and gave him a concussion or five, but it was the greatest thing in his life, those lazy nights.

He saw his hair first, unmistakable as they were, growing out all messy and white from a completely otherwise young body. And his big eyes, similar to his own. Then he obviously saw the rest, how ripped he was and covered in scars and his heart skipped a bit.

He thought then that he was simply excited and concerned at the same time about the state of his skin. He probably screamed his name, but his brother only turned his face slightly, looked at him, and didn't say a word. He just turned around and left.

He followed him, of course, and ran like a dog, talking nonsense. He walked after him, trying stupidly to get his attention. Finally, his brother stopped and said: 'Leave me alone, you stupid cunt."

He was just so shocked that he stopped and let him leave before he found any answer to that .

Well, the last time he talked to him before that, he called him a murderer, so. Well-deserved, but still he was hungry for any scrap of information now. 'How is he doing?'

'You don't know? Well, he is all fine. He is my friend and colleague, fellow Wind Hashira.'

Well, that explained a lot of why people were so over-the-top excited when they first heard his full name. But it made perfect sense. His brother was the strongest person he had ever met, even when they were kids. And he had this fierceness in him that could take him anywhere he wanted. It was only expected that he was one of the best. He felt happy for him even though it made them literally on two far ends of the hierarchy.

'Does he sometimes come over here?'

'To visit me?' She laughed softly and beautifully and he realized that maybe she and his brother were an item. She looked kind and sweet enough. And apparently was strong too. That was someone his brother could've respected enough to… 'No, no, he never visits. Well, maybe sometimes, when he comes along with Giyū Tomioka, that is the Water Hashira. He isn't too social, is he?'

'No, not really.' He said, feeling dry in the throat. He tried to push the treacherous relief out of his mind and not choke on it. He just really wanted to meet his brother again and say him that he is sorry. That's exactly that. He was scared that his brother could come any minute when he was unprepared and he'll then proceed to make an ass of himself. That was all there was to it.

'No worry. He knows that you are here, so maybe he will find a moment in his busy schedule to visit his little brother.'

Somehow I highly doubt that he thought grimly. He had a better chance at meeting him if he didn't know that he was there and jumped on him by accident. Now he would just avoid the Butterfly Mansion like a plague.

'So, the procedure is simple. I'll just take a sample of your blood.'

'And that's it.'

'Yes, that's it. But we will probably have to do it quite a lot of times, so I would be grateful if you stayed here as a guest. One of my girls will show you to your room.'

'Can I… ask for something?'

'And what would be that?'

'I would like to watch how your recruits fight if that's not a problem.'

'No. I have no problem with that.' She smiled.