bakugo katsuki x pro hero sister headcannons ♡
labels. she/her pronouns, y/n is used, reader resembles masaru’s personality.
warnings. light cursing, sibling rivalry/banter, mild violence (sparring), light angst, katsuki being katsuki, occasional soft!katsuki moments, ai used for quirk, light fluff. self indulgent as a older sister lol
as kids, katsuki was always trying to one-up you. if you learned a new move, he needed to master it ten times faster. it was exhausting for your parents, but you secretly loved it.
it started as rivalry—he wanted to beat you. but over time, he stopped comparing and started watching. you were sharp, confident, and strong as hell. and despite how much he grumbled about you being annoying, you were also the reason he never let himself fall behind.
now that you’re both older, katsuki’s picked up this habit of not liking people talking about you in any way that sounds remotely flirtatious. especially if it’s denki. katsuki hates how much denki likes you. it’s hilarious.
❝why the hell was sparky looking at you like that?!❞
❝katsuki. you’re being dramatic.❞
people would stop and stare when you two walked down the street. not just because of the familiar fierce expressions, perfect mix of mitsuki’s striking beauty and masaru’s soft features.
your mom teases that you both get that overprotective streak from her. your dad just sighs in the background and adjusts his glasses.
your mom is insanely proud of you. you’re her clone in all the best ways: attitude when necessary, but calculated grace when it matters. she calls you her ❝perfect little menace.❞
your dad is your soft spot. you’re a total daddy’s girl and katsuki pretends to gag whenever he sees you two reading together or fixing up old support gear in the garage.
sunday mornings in the bakugo household are sacred. you and katsuki make breakfast together—him handling the fire, you handling the precision. sometimes you both burn things on purpose just to irritate mitsuki.
your hero name is miststrike, and your costume is sleek, black and with accents of your favorite color, or just all black, with specialized fabric that helps concentrate your mist in high-pressure areas like your wrists and collarbone. katsuki thought it was badass and totally jacked some design elements for his own.
❝…tch. don’t flatter yourself. i didn’t steal that much.❞
❝your gauntlets are literally based on my fog-chambers.❞
during katsuki’s internship with shoto and izuku, endeavor brought you up while training with him. katsuki nearly exploded on the spot. ❝your sister’s quirk is very controlled and calculated. you’re… emotionally driven.❞
❝don’t compare me to her!❞
he does compare himself to you. all the time.
ignition mist is terrifying up close. slippery terrain, no visibility, and then boom—you snap your fingers and light the whole room up.
your quirk has a strange synergy with katsuki’s. you can trap people in mist, and katsuki can blast them once they’re disoriented. in simulations, you two are basically a nightmare to face. one creates chaos, the other delivers the final blow.
katsuki lives for training with you. you don’t hold back, and he respects the hell out of that. even if it means getting sent flying across the training field.
❝i said go full out, dammit! don’t treat me like i’m weak!❞
❝you say that every time, and yet every time you end up with a concussion.❞
sometimes you train at night, just the two of you. the city skyline in the background, the sharp scent of smoke and chemical mist in the air. no words needed—just shared movement and mutual respect.
there was one time you accidentally overdid it and katsuki slammed into a wall so hard he cracked it. you rushed to him, panicked, but he just laughed like a psycho. ❝you finally got serious. damn right.❞
you nearly cried. he still teases you about it.
izuku calls you ❝y/n-nii❞ and it drives katsuki insane. you’re everything izuku admires in a hero—smart, skilled, and kind to everyone, including him. katsuki gets jealous but pretends not to be.
izuku once made a passing comment like, ❝y/n-nii is so graceful and smart. i wish i could be like her.❞
katsuki almost set the common room couch on fire.
❝shut the hell up about my sister in front of my friends, nerd!❞
❝but she’s so cool, kacchan!❞
kirishima looks up to you the way katsuki refuses to say he does. he always asks for advice about hero work and battle ethics. you always tell him he’s already got what it takes. katsuki scowls every time.
shoto once compared you to fuyumi and katsuki nearly detonated. ❝my sister’s cooler.❞
you use glasses sometimes, usually while working late or reading hero reports. katsuki has a photo of you in them, but if anyone ever sees it, he will literally combust.
he got his love for loud and classical music from you. you used to blast your playlists in your room, and little katsuki would sit in the hallway pretending he wasn’t listening. now he copies your playlists and pretends they’re his.
you’ve got a soft spot for him, even if you act like you don’t. you’re always one step behind him at competitions, watching from the shadows just in case he needs you. he knows. he just never says it.
he still calls you ❝sis❞ when no one’s around.
katsuki doesn’t know how to say he appreciates you, so he shows it in little ways. like handing you cold drinks after training or silently plugging in your dead phone when you’re passed out on the couch.
he actually listens when you give him advice. he pretends not to. pretends to roll his eyes and scoff. but he hears everything you say. especially when it comes to hero strategy or emotional regulation (which he’ll never admit he struggles with)
you’re one of the only people who can tell when he’s having a bad day before he explodes about it. and you don’t ask questions. you just sit beside him, play his favorite songs, and wait. he always ends up muttering something like ❝…today was bullshit.❞ and that’s your cue to listen.
on your 19th birthday, katsuki didn’t say anything until after everyone left. you were sitting on the balcony alone when he joined you, dropped a wrapped box in your lap, and muttered,
❝you’re annoying. but… you’re the reason i’m where i’m at. don’t get sappy or anything. just open it.❞
it was a new set of gauntlets, upgraded and built to compress mist in smaller chambers. custom-made. you cried. safe to say he cried a little too.
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