A/N: Just to reiterate a bit from the book summary so nobody gets confused: For the squad and Muichiro, Reader is around 16. For the rest of the pillars, Reader is around 21. I'll have exactly none of that illegal FBI-Open-Up shit in my book, don't worry. (And later on, for the surprise additions to the character roster, Reader will also be 21 for those.)
And please, if you do ship any of these adults with literal children (as in, they're actually 14-16), please do not mention it anywhere in my books or on any of my profiles. I do not support any of it.
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Tanjiro:
Tanjiro is understandably a little shy about asking you out. But once you accept, his happiness level skyrockets. He'll likely try to take you somewhere nice, but anything is alright in the end -- you may even spend your date taking a stroll around the mountain near Urokodaki's home.
He's a complete gentleman to you the entire time. Tanjiro was raised to treat girls with respect (and with Kie having just as hard a forehead, she wouldn't play around with that) and wouldn't dream of hurting you. He'll give you something before the date, such as picked flowers or something he picked up in a village.
The two of you manage to stay relatively unbothered. Zenitsu caught wind of the date beforehand and promised to distract Inosuke, and Nezuko was roped into helping him (not that she minded).
Nezuko:
Nezuko would ask you the only way she really knows how -- by giving you a gift and getting you to follow her. When you caught on, she'd smile happily and nod -- she wanted to spend time alone with you. (It would be very difficult not to break and fawn over her in the moment.)
Nezuko is sweet and thoughtful. Everything had been thought out beforehand (with her brother's help), whether it be a little moonlit stroll by the river or a dinner date at a cute little restaurant. She'd make you take your katana just in case someone (or something) interrupted you.
The two of you would be relatively unbothered by humans, at least. Zenitsu and Tanjiro promised to leave you alone (although Zenitsu was a little sulky about not spying on your date), and Inosuke didn't really care. Whether you get attacked or not is out of your hands, although you do exercise more caution on your date night.
Zenitsu:
It would take some hyping-up to get Zenitsu to finally ask you out, but when he does, expect that he'll try to treat you like a princess. He's far too sweet for his own good, and you sometimes have to dissuade him from doing more expensive things for you, like buying you a new necklace as a gift or taking you to a fancy restaurant in the city.
Of course, he's 120% a gentleman the whole time. He's really nervous about something going wrong, but your laid-back demeanor will do a lot to calm him down. Humor is a must, even if it ends in him laughing a little too much at every joke you make. Eventually he'll feel comfortable enough to enjoy the date.
He already made Tanjiro promise to leave you both alone for the date, and Inosuke really didn't care. The Kamado siblings are just happy to see you two getting along so well.
Inosuke:
It will take a few suggestions for him to finally ask you out somewhere. Inosuke is really stunted when it comes to romantic gestures, so if you both end up doing something like walking in the mountains, give him a little slack.
He'll likely be a little awkward about it until you break the ice somehow, though once he gets more comfortable he'll grow more confident in himself. His idea of a good time might be something like getting a big fish to roast or letting off some steam at a hot spring (don't worry, he'll likely not care about whatever you're rocking under your clothes and will respect your privacy to a degree). Praise is a must with him, because there's a first time for everything, and Inosuke hates looking like a fool in front of those he admires or cares about. Just let him know that you're enjoying the activity and that he's doing good, and you're set for a happy boar man.
Tanjiro and the others already promised to leave you alone (really, Zenitsu swore up and down that he wouldn't disturb you two even if he were dying; dramatic, but on-brand). Tanjiro seemed happy enough that you two were getting on so well, and Zenitsu was just happy that Inosuke was mellowed out for a while.
Giyuu:
It'll take a few encouragements for him to make a move. Giyuu doesn't know much about dating, and he'll probably have to be all but drop-kicked through your door with flowers and a sign that says "Please go with me to (insert location here) on a date". Even then, he'll be incredibly shy about it -- not stuttering, but very quiet.
When you say yes, he'll relax somewhat, but still be a little tense while you're on the date. He really, really doesn't wanna mess anything up. Whether it's a quiet walk somewhere or a picnic or even a cute little boat on the river, he wants everything to go as smoothly as possible. Just enjoy yourself and he'll unwind.
Usually none of the others will come near you two on a date. Shinobu may check in once in a long while to see how you two are getting on, but the rest don't really care (except for Mitsuri, who usually accompanies Shinobu).
Kyojuro:
When he has free time, he'll ask you to go on a date. He's pretty casual about it (well, as casual as Kyojuro can be about things), just happy to be with you for the day. He shows up at your home with a (f/flower) and asks you to go with him.
You'll end up doing something peaceful, like sitting by a river or taking a hike up the mountains. He likes to unwind with activities like this to remind him about life outside being a pillar. He likes to take you with him because you're special to him and he wants you to be a bigger part of his life. It's all really sweet. You two end up at the summit with a blanket and a lunch basket, spending the afternoon eating, laughing, and talking.
The other pillars usually agree to let you two have your time alone, even Mitsuri (although she's a little pouty about not being able to see you two 'in your element' as she describes it).
Muichiro:
Muichiro can be a bit spacey at times, so don't be offended if he mentions a date offhandedly or if he forgets to ask you. He's still a little nervous to ask, and may put it off just because it's stressful.
The two of you will probably go on something low-key. Birdwatching is fun on sunny days, or you may sit by the river with snacks and just enjoy nature. Muichiro likes to rest his head in your lap as you tell stories. Your voice is soothing enough to put him to sleep.
Usually the others agree to leave you alone. Tanjiro takes the others somewhere while Mitsuri just spies from a distance (but rarely).
Shinobu:
As soon as Shinobu finds some free time, she's taking you on a date. Be prepared for her to be at your doorstep wanting to take you out somewhere.
If you're lucky, she means to take you to a nearby festival or hot spring for a day of relaxation and fun. But sometimes she means letting off some steam at karaoke or taking a run through the mountains. She can be very mischevous when it comes to what she wants to do; usually you have no idea what she's planned until you get there.
The others don't really get involved with you two (unless you two end up going to the Butterfly Estate). Mitsuri is especially happy for Shinobu and may very rarely check up on you (from a distance) with the butterfly girls.
Gyomei:
It may take him a while to ask you, mainly because over time he's come to see you as a true ally (and almost like one of the children at his temple). But when he does, he asks you if you would accompany him somewhere (with your parents, embarrassingly, watching from around the corner).
You end up doing something quiet, like sitting somewhere and talking or (on very rare occasions) watching the full moon from the safety of your garden. He may cry a little during the date, but it simply means he's honored to be with you.
The others won't interfere, mostly because either they don't care or they respect Gyomei enough to let you two be. (Usually it's a fusion of the two.)
Sanemi:
He'll be very stubborn about it, but after a kick in the pants (maybe by a certain hanafuda-earring-wearing Kamado boy, and quite possibly literally), he'll basically shout at you to go on a date with him, blushing the whole time.
What you do is random. Sometimes he'll take you to eat somewhere, sometimes he'll take you out to a bar to get turnt. He's not very picky about what you do, mainly because he doesn't know what to do on that front. He's pretty clueless the first couple of times, but when he finally begins to relax, he notes what you especially like and tries to take you to those spots. (You two go out drinking quite a bit.)
The rest don't bother you two. Either they're intimidated by Sanemi, they don't care, or they just have better things to do.