A/N : As you know, I'm back to Law school, and work has been hectic. That's why I wrote a headcanon instead of a scenario, I'm so sorry. But I need to focus on the Muzan requests too so I can deliver some quality too ! (and also on the 20 analysis I have to do in 7 days-)
Tanjiro
❀ Tanjiro isn't afraid of words, even though in his opinion, none could truly measure the amount of feelings and images you inspired him. Ineffable, his world was . In that regard, he wouldn't be afraid to clearly state the three words you longed to hear : « I love you ». Hell, he would tell you the most beautiful words, at the most unexpected times, though he would never understand why they were not appropriate times : to him, every second of life was a second worth telling you how much he loved you.
❀ He would always compliment you when you need it the most. Calling you beautiful when you thought you weren't ? Yes, he would. Calling you brilliant when you doubted your abilities ? Yes, he would. Cheering you up ? Of course. Tanjiro will immediately feel it when you're in need of support. And as your knight in shining armor, he would never allow anyone or anything to tarnish your world, as it was also his. He would walk through the gates of hell if it meant fighting all of the demons that dared shielding you from the happiness you rightfully deserved.
❀ He would always protect you, no matter the cost. He would go through a field of professional snipers if it meant offering you a chance at living.
❀ Where words were not an obstacle for him, physical contact would. In fact, it would be very difficult for him to initiate contact ; embraces, kisses, cuddles, holding hands. It's not like he never wanted it ; quite the contrary. His heart ached for the proximity he could embrace close to yours, and the warmth radiating through your carnal envelope. Even if he was more at ease with words and actions, it didn't mean that his kisses wouldn't radiate love and adoration. An exquisite tint of rose would delicately color his features once you would come closer.
❀ He would proudly show you off to the world, his eyes filled with the brightest constellations when he told the ones around that here was his soulmate, standing as the warmest source of light in the entire universe, as the purest form of life in the darkest valleys. Nevertheless, he wouldn't be a territorial partner and would never once take you for granted ; and reminding you of how lucky he was to have you was the least he could do.
Zenitsu
❀ Zenitsu would be your biggest fan ; there wouldn't be a day where he wouldn't fawn over all the smallest things you achieve so effortlessly. He felt like you made the angels themselves blush in envy and made it all seem so easy. He would never let Tanjiro or Inosuke pass without letting them know how much he adored you, and how supernatural you were.
❀ He would use a lot of pick up lines and stereotype-ish gimmicks to get your attention, which would result in you laughing with a profound cherry color on your features. In fact, Zenitsu would do anything to distinguish even the smallest smile on your face, the one sending the Heavens to shame, the one enlightening the deepest abysses of Hell. He would ask you to marry him, and he would rehearse his vows every day in front of your window just so you would understand how much he cared.
❀ He would try to not fawn over other girls. It would take him time, but making efforts is to him the best proof of love, and it just showed how much he cared about you. He wanted to be a better man as he finally had found the missing piece of his life puzzle, which would make him work harder to become worthy of you. So much he would love
❀ Zenitsu loved pecking your cheek. Anytime he could steal one, he would, and this at the most unexpected times. It would send his own heart fluttering, meaning he would have a harder time kissing you, as his face would turn a genuine shade of crimson.
❀ He would tell you he loved you every morning once you woke up, the sunlights inspiring him to cover yourself with undying passion. He wouldn't say it in front of your friends, as it was to him something very intimate, and even though displaying PDAs wasn't too much of an issue, this to him was completely different. He would make sure you two were alone when it came to that talk.
❀ Did I mention he will cling onto you most of the time ?
Inosuke
❀ Inosuke was thrilled to have a partner of his own, and he was eager to learn how to love. Because of his past, it wasn't something he was an expert at ; but his sense of observation was one of the best. In that regard, he would pay real attention to you, which lead to him trying to get your attention at all cost. He would ask you a lot of questions in order to learn how to impress you and how to know you. That's how he would display his love ; by learning how to. He would go through endless and painful hours of talking with Zenitsu just so he could learn how to be perfect for you, and better than the others.
❀ He will always ask you if you liked what he was doing ; did you enjoy him stroking your hair ? Did you like it when he held your hand ? Or when he hugged you from behind ? Would you rather have him kiss you on the lips or on the cheek ? He was genuinely trying to do his best to become a bit more « human ».
❀ To him, words weren't as meaningful as actions, since he never had heard of their power. Therefore, his demonstration of affection would mostly consist in him « grabbing » your hand instead of holding it, standing before you in case of a threat, spinning you around with a hoarse yet silly laugh just so he could get a reaction from you. When he was laying next to you, he would always have his arms wrapped around your waist, just making sure you weren't just a dream but a loving reality.
❀ He would be quite clumsy, as his agressive nature was became a facade he used to hide what he could feel. He would yell at you quite oftenly or sometimes even laughing at you. His words would be harsh, but they truly didn't mean no harm. You were the most beautiful thing that happened to him, like the breath of an angel caressing his skin, and the truth was that he was terribly scared you would abandon him one day.
❀ He would steal a necklace from a jeweler's to give it to you, and he didn't understand why you were mad at him from bringing you a gift, which confused him at best.
Giyuu
❀ Giyuu's habit of self depreciation would be a very difficult obstacle to take down in order for him to conventionally show how much he loved you. Therefore, he was quite afraid his lack of experience and power on that issue would cause you to leave him ; and this would be the death of him. His thoughts were filled with the most delicate poems and flawless metaphors, the colors you shed to his world turning into the most beautiful painting he knew wouldn't represent half of your beauty. So how would he show it ?
❀ Giyuu's words weren't the smoothest, but he was honest ; and his sincere demeanor would be the best representation of what a relationship was to him, a collaboration and a place of no-judgments. He would always be there to listen to you and give you honest, sometimes harsh, advices to carry you all the way. He was your pillar, the one helping you stand straight, your balance.
❀ He wouldn't tell you « I love you » a lot, but the way he would move you from the sidewalk if a car drove to close, the way he would wrap his arms around your waist when a lot of people walked by, or how he would always cover your sleeping body with his own haori at night, would definitely make up for it. Words were beautiful, he thought, but they wouldn't mean a thing if no actions were following. Though, his usual and multiple « Be careful », that sounded like threats, would mean more than the few romantic confessions he could let out.
❀ Even though he wouldn't be very keen on physical contact, there wouldn't be a moment in the day where his fingers won't intertwine with yours ; grazing the tip of them, caressing the top of your hand, immortalizing its warmth so his own body would remember it. He loved wrapping his hand around yours when you would ramble about everything and anything. If he was in the mood, he would bring your hand to his lips, pressing a soft kiss on it, so soft, but warm.
❀ Hell, when he felt like you still doubted his love for you, he wouldn't hesitate to use greater weapons. (A/N, check the Passion chapter if you haven't.) Indeed, he won't hesitate to claim your lips with unveiled passion, trapping your form with his, covering you under genuine care, like protecting a flower from pouring rain.
❀ He would always squeeze your hand tight before letting it go to fight, the warmth of your palm imprinted on the hold of his sword ; because fighting for you was the best way to demonstrate his love for you. After all, you were the only reason for him to live, so having this reminder was the perfect way for him to also remember that you loved him just as much.
Muzan
❀ Muzan would do whatever it takes for you to understand that you belonged to him, and him only. It was more than displaying feelings, it was a need for him to create a constant reminder that you were his own discovery. If you were both in public at that time, his pale hand would never leave yours, and his eyes would dart around the ones that dared trying to get a glimpse of your angelic beauty.
❀ Grand gestures would be part of the package. Love wasn't in the details, at least to him ; love was everywhere. And the entire world needed to be a reminder of what you shared. He would love offering you your favorite flowers, letting them in front of your door so you would wake up to his undying passion.
❀ Indeed, he knew you weren't a demon, and the time difference it implied gave him an idea ; he would come at night so you could fall asleep by his side, and before the sun set the moon to sleep, he would lay flowers to your front door, or love notes. His world and yours were opposite, he was the shadows and you were the light. But he adored you so much he knew he wouldn't bare it if he hadn't tried everything to make them collide.
❀ He would perfectly know what words to say, where to caress you, where to kiss you, hell, how to look at you, to make you feel overjoyed. You were like the beat of his favorite song ; he would recognize it among thousands other, and would never be able to forget it. He knew all of you, all the details you didn't even notice in your own self.
❀ Muzan would be very physical, intimate. Sleeping next to you will involve cuddles and more once he made sure you allowed him to. If you were insecure about your body shape, he would make sure his thousands caresses and careless whispers took away all of your worries. He adored you, worshiped you, even if it all started as a game to him since he needed your trust, he knew he wouldn't be the same without your presence. And he hoped his unusual warmth would let you know about it.