alternate title: when they realize they want to spend the rest of their life with you <3
this is a little different than my usual fillers but i rlly liked this scenario idea lol
also i decided to not write in the usual headcannon format this time, hope y'all don't mind :)
Tanjiro Kamado:
When you and him cuddle.
Just the simple, mundane action of embracing one another fills his heart with pure, unadulterated love for you. Just feeling you relax in his arms is enough for him to know. Just for him to realize that you're comfortable enough and that you trust him enough to fully relax in his arms is enough for him to know and realize that you are and always will be the one for him.
Zenitsu Agatsuma:
When you take a bath together.
To trust him enough to put yourself in such a vulnerable spot makes him so completely joyful. There's nothing sexual about it to him. It's only about the intimacy of bathing together that fills him with so much joy. You trust him. You trust him so much. He never thought that anyone would ever trust him as much as you do. You're the one for him, he knows it. If he can help it, he will never break that trust.
Inosuke Hashibira:
When you clean his wounds.
He's not necessarily sure why but...whenever you clean his wounds for him after a mission, he feels so...loved? Appreciated? He's not exactly sure. Maybe it's the vulnerability he feels during those moments as well as the trust he gives you. He's not one to trust people easily. You're an exception. He hopes that you'll be the first and last person to help him in those critical moments.
Giyu Tomioka:
When you kiss him.
Evidently, Giyu's life hasn't been the best. He's gone through numerous hardships. And evidently, he hasn't had much motivation to do...basically anything. Though, of course, there are a few exceptions such as his friends. But the moment he met you, he was overcome with so much...strength. He tried his hardest on basically everything he did. Missions? He'd finish them as quick as humanly possible so he could come back to you quickly. And if he was lucky, if he outdid himself, then he'd receive a kiss from you. Evidently, it was his favorite part of the day. Your kisses were enough to keep him going and so, he knew you were the one for him.
Sabito:
When you say his name.
Many people have said his name in his lifetime. None of them really made him feel anything, though. Why would they anyway? It's just his name, nothing special. But the way it just rolls off of your tongue so perfectly makes him swoon. You've got him wrapped around your finger and you don't even know it. He's so utterly and hopelessly whipped for you, he'll do anything you say no matter how ridiculous it is. He wants to spend the rest of his days with you. He wants to grow old with you and hopefully hear you say his name again and again until he takes his last breath.
Yushiro:
When you gather herbs with him.
It's not necessarily the herbs. If it was it would be weird, to be honest. It's probably just being able to spend time with you. Yeah, that's it. Being in your presence is enough for him. He awaits the moments he can bask in your precious presence. Though he will admit, being alone with you increases his affection tenfold. It's the privacy of it all, really. He wants to share special moments with you and only you. You're really, really special to him. He hopes he can have forever to show you that.
Muzan Kibutsuji:
When you treat him like a regular person...or demon in his case.
We all know Muzan. He's...well, Muzan. The Muzan Kibutsuji. A demon feared by many. Though his significant other isn't scared of him. If anything, Muzan's scared of them. He's so scared of messing anything up. You're so different to everyone else. You treat him so...normally. You treat him as if he isn't one of the oldest, strongest, and most feared demons out there. Muzan must admit it feels nice. He's not sure what he would do without you. You make him feel so, dare he say, happy? Yeah, you do. You make him really, really happy. He hopes he can make you happy as well.
Kyojuro Rengoku:
When you play with his brother.
Family is important. It's very important to Kyojuro. You are a part of his family. Though, whenever he sees you bond and play with his brother, it fills him with such warmth, he can't describe it. Seeing you get along with his brother makes him really happy. He knows he's chosen right, he knows that he has made the best decision in his life. But ultimately, he knows you are the one he wants to grow old with.
Muichiro Tokito:
When you're patient with him.
Muichiro gets distracted a lot. He's not sure why. Though sometimes, he can't help but be mesmerized by nature. Sometimes when you're both out on picnics, he'll catch a butterfly fly by. Immediately, his eyes lock on. The colors are so pretty. Is it a monarch butterfly? The shade of orange is gorgeous. Oh look, it stopped on a flower. Oh it flew away, bye bye butterfly. Right, what was he doing again? Oh yes, the picnic! He turns and looks at you. You're looking at him? You have a smile on your face, a really pretty smile. It makes him smile too. You never get mad at him for it, even if he gets distracted 5 times throughout your picnic date. That's how Muichiro knows there's no one else for him.
Akaza:
When you kiss his injuries.
Akaza is quite the reckless demon. He's sorry, really, he is! He doesn't like seeing your smile drop when your eyes land on his injuries. He knows that you're aware he's a demon and that he can heal abnormally quickly. Though, it doesn't stop you from leading him somewhere to sit and clean them up. Even as his injuries begin to heal quickly, it doesn't stop you from kissing wherever he's been hurt. It elicits his cheeks to turn a red shade, he avoids eye contact. He will never admit it but he really looks forward to your kisses.
Obanai Iguro:
When you take care of Kaburamaru together.
Kaburamaru has been Obanai's companion for quite a while. Obanai cares about the snake dearly. Seeing you care for his snake companion makes him feel...weird. He's not sure why though he does like it. It makes him feel happy that you get along with his long-time companion. He very often joins you. But sometimes, he just watches from a distance for a bit to admire the moment. He ingraines it into his brain, wondering what he'd done in a past life to have someone so...caring, before eventually joining you. These moments are ones he cherishes most.
Tengen Uzui:
When you help him relax.
Tengen works hard. After a long day, all he wants to do is flop down on his bed and sleep for the next 4 days. Whenever he sees you it's like he's suddenly rejuvenated, he feels like he's just drank enough cans of red bull to fill an entire trash bin. He immediately clings to you, trying and failing to stay up right and he ends up putting his entire weight on you. You both fall. After you've both laughed it off, he'll finally get up and help you as well. After a rough, long day, you prepare a bath for him and make him a meal. He deserves it, he's worked hard. He never asks you to do all of it, he would much prefer to just lay in bed with you. He won't complain though. In his mind, he's already planning how to return the favor.
Sanemi Shinazugawa:
When you hug him.
Sanemi can't remember the last time he was hugged. He doesn't really care though, or so that's what he tries to convince himself of. Truth be told, sometimes he wishes he could be held in warm arms. Alas, he'd come to terms with the fact that he would probably never experience a warm hug ever again. Until he met you. He never would have guessed he'd take such a liking to you. He never would have guessed he'd be able to experience what your arms wrapped around him would feel like. He doesn't complain. He merely wraps his own arms around you and buries his face in your neck. The way he squeezes you back feels as if you're stuck there, in his arms. That's because he never wants to let go. He hopes you feel the same.
Douma:
When you tell him you love him.
Douma hasn't been able to feel many emotions for as long as he can remember. He's not too troubled by it, however. He'll admit even after meeting you, he still didn't feel much. Though sometimes, he can feel just the slightest squeeze in his chest, or the slightest turn of his stomach, or also the way his face burns when he sees you. Those feelings increase tenfold when you tell him you love him. He never thought he'd feel anything, much less to those 3 words he thought he'd never hear be directed toward him. Douma loves you, truly.
Genya Shinazugawa:
When you make him feel safe.
In a world where demons roam, killing and feasting on humans, Genya never thought he'd ever feel safe. He doesn't know the science behind it, if there is any, but just seeing your face after a tough day makes him visibly relax. You don't have to do much, just cuddle with him, have dinner with him, or shower with him and he'll feel safe. He'll feel the safest he's ever felt in his life. As he rests his head against your chest, as your fingers thread through his hair and massage his head, slowly lulling him to sleep, he hopes that someday he can make you feel safe as well.
Hotaru Haganezuka:
When you indulge his rambling.
You don't know jack shit about sword making or being a swordsmith. But that's why Hotaru's there! He'll teach you every single detail about the process that is making swords. He can't help but just ramble and rant on about the struggles and the rewards of making swords for demon slayers. He could go on for hours. And he does. He gets so lost in his rambling, he doesn't notice how softly you look at him. And you let him ramble on because seeing the look of utter happiness on his face and seeing the way his eyes light up as he talks about the things he enjoys makes you happy in return. Yeah, Hotaru's sure of it, you're the only one for him.