Work Text:
You jolt when your father touches your shoulder to see your progress in decorating; you’ve been baking all morning.
Aizawa chuckles, low and scratchy in his throat before dipping his finger in the glaze to taste it. Despite not looking or acting like it, your adoptive father’s sweet tooth is quite demanding. He hums, “the lemon’s pretty strong.”
You nod determinedly, “well, the biscuit’s really sweet, so they’re supposed to balance each other out!”
Aizawa hums and squeezes your shoulder again before reaching for the pot of coffee to pour himself a cup, “and you’re sure you want to stay and meet them? You’re always welcome at work and hang out in the office.”
You’ve hung out in the teacher’s lounge plenty of times at this point; Aizawa agreed to home school you the first year that you lived with him and Shinsou so that your focus could be adjusting to family life. Now the year’s close to over, and you’re all looking for ways to make you less anxious around other people.
Shinsou inviting his friends over for video games are one of those attempts.
You shudder when you think back on Shinsou’s promise to reward you if you do well today. It’s the main reason that you’ve decided not to back out and hide at Papa’s work like Shinsou often teased you for doing. You square your shoulders and nod, before you finish decorating the biscuits, barely saying goodbye to Aizawa before he leaves for work.
They all arrive at the same time. With your father gone you’re standing nervously in the kitchen, unsure when to approach and greet them. You flinch when your brother calls your name, waiting a beat before gathering your courage to walk into the entrance hall.
They all smile and loudly greet you; you hide behind Shinsou at the noise and a pink girl immediately apologizes and turns around to yell at the group of guys to be more quiet.
They introduce themselves as Bakugou, Kirishima, Sero, Kaminari and the girl as Ashido. Bakugou looks angry and speaks in a strained but soft voice and Kaminari smiles at you in a way that makes your palms sweat. Kirishima and Sero both lower their knees and gives you a high five like you’re a child and Ashido gives you a hug without asking.
“And this is my baby sis,” Shinsou says as he pushes you a little further, trying to make you say your own name. It comes out in a stunted effort, but the entire friend group just coos and yells out, “babyyy!” mocking the way Shinsou babies you. It’s a joke that started between them during one of their online gaming sessions. You relax your shoulders at hearing something familiar from the group.
They’re gathered around the couches playing Super Smash Bros with you on the armchair. They’ve all complimented your baking. Bakugou came with a very constructive critique and commentary on the structural integrity of the baked goods while Kirishima gushed about the glaze you’d put on half of them. Sero and Kaminari fought about who could fit the most in their mouth while Ashido kept count.
“Do you wanna try?” Kaminari asks after conceding his loss to Sero and swallowing a very dry amount of biscuits with a big glass of water, pointing the Switch controller at you.
You wave your hands, “oh no, I haven’t played a lot of games. I would just ruin your stats.”
Shinsou smiles at the buzzword you’ve picked up about gaming without understanding the meaning. Kaminari shakes his head and pats his lap, “come on baby sis, I’ll teach you! Hey Kats, you’re out this round, you don’t know how to be nice.”
“Hah? As if I’d ever coddle anyone.”
Despite saying that he still hands his controller to Kirishima. Kaminari pats his lap again and you look to Shinsou for affirmation; is this okay?
He nods and points to Kaminari with a promise, “if he bites, I’ll punch him.”
It makes everyone laugh as you get up and dusts off your skirt before walking over to the blond. He spreads his arms to take you in and you yelp when he wraps them around you after sitting down. He holds out a blue controller in his hand and urges you to grab it. Then he puts his own hands on top of yours like your brother’s done before, and tells them to start the next battle.
Whatever game Shinsou has played with you before is not nearly as chaotic and fast paced as Smash Bros, and Kaminari’s definitely doing 90% of the playing for you, with the way you keep losing your character on the screen.
He’s warm, and whenever he laughs or talks behind you, the hairs on your nape stands on end. His arms are rested around your waist and it feels like he sometimes squeezes you a little though you’re convinced it’s your imagination. When the battle’s done he leans his head unexpectedly close to your neck and kisses you so quick that you’re convinced you must’ve imagined it.
“Well done, baby sis! Want to try again?”
You stutter, reeling from the game play and his actions. Warmth gathers in your stomach and your breath quickens as you nod before you’ve realized it. “Good girl,” he praises next to your ear, “I’ll be closer this time to help you,” he half-whispers and jokes in your ear, and you hope he doesn’t hear the sigh that escapes you at his actions, leaning your back more into him. You shudder every time his arms squeezes you.
You don’t win any rounds at all, but everyone – except Bakugou – praises you as if you’ve won a gold medal. It makes warmth settle in you and your shoulders fall to a relaxed position. When you gather the courage to compliment Ashido’s shirt, she excitedly pipes up,
“oh you like this sort of style? I have plenty of clothes at home I don’t use anymore! What’s your size? Maybe I could bring it sometime!”
You’re exhausted in Shinsou’s bed when night comes. You blearily remember falling asleep on the couch after saying goodbye, and Aizawa coming home, asking you to brush your teeth. They’d both laughed at you falling asleep standing by the sink.
Shinsou has a night shift at the Agency, and leaves you to sleep in his bed, promising he’ll be back before dawn. You hug his pillow as your breathing gets heavy again. You’re glad everyone enjoyed your baking and thought it was fun to play with you. Kaminari was especially sweet to you, in a way that felt similar and safe as your precious big brother – warmth settles when you imagine him hugging you goodbye like he did when they left. You fall asleep with a smile.
____
It’s been a week since then, and Shinsou still hasn’t rewarded you. Aizawa’s schedule ended up similar to Shinsou’s and you’ve had little time to be alone. Today, your adoptive father’s having a triple shift; a day-shift at the school, afternoon patrol and a night shift at the dorms. Shinsou’s in his bedroom playing with Sero, Kaminari, Bakugou and Kirishima.
He promised that he’d have time for you at 4PM.
It’s now 4.28PM and he still hasn’t made any intention to log off the game. You stand in his doorway with your arms crossed, fidgeting with your feet on his carpet. You try to hide a pout but it’s getting harder the more impatient you get.
“Wanna play another round?”
You sigh when your brother’s the one offering another round to his friends and decides that no matter what, you deserve to be rewarded; both for your patience all week and your courage last week.
So you do something bold, something Shinsou hadn’t predicted but wholly welcomes. You throw off your shorts and underwear and pull at his desk chair and crawl onto your knees, trying to quietly sit under his desk.
“That’s a nice spot.”
Your brother continues talking with his friends as you settle, but he looks down at you with a challenging smirk and you like to think that you’re gaining his approval with your actions. He moves the left side of the headset to the side, so that he can listen to you.
With annoyance still seething in you, you start to paw at the crotch of his pants, feeling his half-hard cock growing under your touch. Your eyebrows are furrowed and teeth clenched as you start to unbutton and unzip his pants. He adjusts in his seat to make it easier for you and spreads his legs farther.
“We have to be quiet in here.”
You don’t know whether or not he’s talking to you or his friends but you decide to heed the prompt anyway as you pump his length. It’s hot and heavy in your hands already and your brow relaxes when you see the first drop of precum dribble out of him. You lick your lips as you think about his taste, your thumb going over the slit of the angry red head.
He clears his throat in between commentary of his gaming and it falls coincidentally with all the times you tighten your grip or twists your hand just right. He’s taught you what he likes and you’re using it to your full advantage right now.
Your brother chokes for a split second when you take him in your mouth; you take him as far down as you’re able and stay there. You’re drooling as you focus on your breathing. His scent is heady and addicting and you’re already feeling cross-eyed from just tasting him. Your pussy throbs as your jaw aches.
“Ye-yeah, we can do another round.”
He sounds more hesitant this time, less enthusiastic. He keeps giving you quick glances to see if you’re going to move, and smirk proudly at you when you don’t. Halfway through a round he suddenly thrusts up into you, making you gag in surprise; the spit gathered in your mouth comes out unexpectedly and you whine when you see the thick string of saliva connecting you.
“The cat, sorry. She must’ve gotten too many treats,” Shinsou says into his headset, “eew, Denki that’s nasty.” he adds before a quick free hand comes down to pat you on the head, like a silent are you okay?
You reply by licking a stripe up his slimy and soaked length, adding extra pressure on the vein popping out. He lets out a string of curses and you’re unsure whether or not that was because of the game or because of your actions.
You take the fat head of his cock into your mouth again and sit back prettily, tapping his knee to let him know that he’s free to move.
With a sigh so quiet that you don’t think the mic picked it up, he lazily starts moving in and out of your mouth. Your jaw has started to ache on the edge of painful but it only adds to the excitement that you’re pleasing your big brother. You clench your thighs to give yourself some relief.
Shinsou’s bickering with his friends about loot and safe areas continues while he enjoys his little sister’s perfect mouth. Your gag reflex has improved drastically since the first time you sucked him off and Shinsou’s noticed how just having the fat weight of his cock in your mouth, cock warming him, almost seems to be enough to get you off. He’s waken up more than a handful of times in the morning with you suckling on him like he’s your pacifier.
His dick twitches in excitement when he pushes just a bit further to feel your throat tighten around the mushroom head of him and his own eyes roll back when he feels your spit crawl down over his balls and making a mess of his pants and the desk chair. Your small mouth must be absolutely dripping and if he weren’t in the middle of a big shootout, he’d definitely roll his chair back to see your face, blissful and full of your favorite cock.
He has half a mind to tell his friends to shut the fuck up so he can hear you sucking him off sloppily and moan at him.
Shinsou almost comes right then and there when he realizes one of your hands is between your own legs. It’s rare that you touch yourself without him asking you to and it’s at that moment that he lets his character die and groan. He pretends it was an honest mistake and sighs at your warmth, “well, let’s call it.”
Sero boos at him and Bakugou barks out complaints but they fall on deaf ears as Shinsou picks up his phone to shoot Kaminari a quick Discord message: stay in the voice chat after everyone leaves.
Before putting down his phone though, he opens the camera and aims it down at you. When you realize, you whine softly and lift a hand to hide yourself. Shinsou chuckles and locks his phone. Maybe another time. He says his goodbyes to his friends and shuts down the game.
He turns down the volume on his computer so that there won’t come any sound out of his headphones before he puts them around his neck.
“Hey baby,” he says as he reaches out for your cheek. You immediately lean into your brother’s touch with a shaky sigh, like a devout believer being graced by their God. With his thumb he draws gentle circles onto your cheek as he uses his other hand to direct his cock around your face. You giggle at his actions and chase it with your tongue.
“C’mere,” he chuckles as he takes your hand and pull at you to join him. He pushes his chair back and pats his lap so that you can situate yourself there.
“Well, aren’t you an impatient princess?” Shinsou asks as his hands finds purchase on your ass, kneading the cheeks. You hide on his shoulder, closer to the mic than you know, and moan. Finally, your brother’s attention is on you.
“Onii-san,” you moan as your brother kisses the crown of your head, “I need you,” you whimper, your mouth hanging open, the control of your jaw feeling lost to you right now.
“Yeah? Couldn’t wait until your big brother was done playing?”
You shake your head with a whine, your thighs quaking from the excitement running through you, trying to figure out if it’s okay to grind your hips against your brother. He chuckles, “you really are spoiled, aren’t you?”
You’re about to protest, to give a pouty, cheeky remark, when one of the hands kneading your ass reaches your pussy, pushing in two fingers without warning. Shinsou hums when your soft and pliant pussy opens up easily, “so you tried to prepare yourself, hm?”
You moan when your brother curls his fingers inside of you, reaching that spot with ease before he scissors them. As you moan into his collarbone, Shinsou steals a glance at his monitor to confirm that Kaminari’s definitely still on the call.
“Is this the reward you’re claiming, baby? From last week?”
“Uh-uh,” you moan as your hands clench around your brother’s T-shirt, your hips pushing yourself back against Shinsou’s hand, “’been so lonely and empty all week, Onii-san. You promised me I’d feel good if I met your friends.”
He coos at you, “aren’t you feeling good right now? Are you saying I lied?”
“Noooo,” you whine, “’s just, I had to ask for it myself.”
Your pout is so cute as you look at your brother; your face is flushed and your pupils blown wide as you try to look annoyed. He kisses you as he pushes in past his knuckle, the wet sounds of your pussy filling the room as your tongue tries to keep up with his. He hopes the mic catches it – he doesn’t doubt that Kaminari’s turned the volume all the way up.
“Did you like my friends?” he asks as he pulls away, his voice hoarse and low and a shiver runs down your spine before you nod, “mhm, they were really kind to me.”
“Yeah?”
“Yeah,” you sound out of breath as all you wanna do is focus on your brother, but you can feel that he wants you to talk, to tell him how you feel. With a spark of annoyance in the disruption of getting him inside of your soaked cunt, you push hard onto his hand before you add, “I really liked the blond one. He was nice to me.”
“Bakugou?”
You know he’s messing with you and when you look at him with furrowed brows, you see a teasing glint in his eyes, “no. The one with the streak in his hair.”
Shinsou hums before his other hand snakes in between you to circle your clit. You gasp out and arch your back.
“You liked him? Did Denki-nii treat you alright?”
The way that your greedy pussy tightens around his fingers tells your brother all that he needs to know. He chuckles and leans into your ear, “I think Denki-nii really liked you too.”
You moan and kiss at your brother’s jaw, “have you thought about him this week?” Shinsou lets you lap at him like a puppy as he pushes in and out of you in a controlled pace, his fingers soaking wet. You suck him in so easily, so happily that if he weren’t playing a mind game right now, he’d be fucking you senseless.
But he needs to finish this game first.
“Did you think about having him in here?”
He bends his fingers again, massaging you. You whine and hide in his neck again, “mhm,” you admit. You feel dirty for admitting it, embarrassed and wrong.
You’re convinced that your big brother will be angry about this.
But you’d never dare lie to him.
“Yeah? You want Denki-nii to fill up your pretty little princess pussy?”
It’s embarrassing, the way that you’re humping your brother’s hand, thinking about his friend. You’re drooling onto his shirt when you admit it, “’did think about it but…” you moan when his other hand adds pressure onto your clit that has you seeing stars, “’did think it but this is Onii-san’s… Onii-san’s pussy.”
Your brother tuts at you but relieves the pressure on your clit, “you don’t wanna share Onii-san’s pretty hole?”
You shake your head and repeat the words no and never, begging him to understand that you’re his. You’re Onii-san’s and only his. You don’t want anyone else to change the shape of your precious hole. Only your brother’s cock is allowed in there.
Shinsou sighs and you fear he's disappointed in you and you have to hold back your tears, but then he calls your name, “look at me baby, can you look into my eyes?”
You’re afraid to do so, but you trust him. With shaking shoulders you lift your head to look him in the eyes, surprised to see him smiling, full of love. Love for you, only you. He’s about to open his mouth and say something, but you lean forward desperately to kiss him, to be kissed by him, to feel the love you saw in his eyes.
And he gives you all of that and more. He licks at your lips, your tongue, your teeth and fucks your mouth with his tongue, making sure you understand that he’s not angry.
“I won’t let anyone touch your baby pussy, I promise,” he says when he pulls back. You look so relieved that Shinsou’s cock twitches, still hard despite being neglected.
“But don’t you still want to be close with Denki-nii? I know he really likes you.”
He kneads your ass as he steals another glance at the screen; Kaminari’s still on, probably fucking his hand at this moment and confirming that he does indeed want to fuck Shinsou’s little sister.
He’s decided that he’ll let him.
But not where you don’t want him. So Shinsou takes his fingers, soaked from your needy cunt and starts circling your puckered hole with his middle finger. You look back and whine, “Onii-san, what are you doing?”
You sound worried, like the first few times he did something new to you, but you don’t move your ass away from him, nor does your grip on his shoulders tighten, “that place’s dirty.”
Shinsou tuts at you, “didn’t you want Denki-nii to feel good as well?”
You actually hadn’t confirmed whether or not you still wanted him, but that mattered little to Shinsou at this moment. As he slowly starts pushing in and out with just the tip of his finger, teasing the hole, you look at your brother, eyes begging for guidance,
“Will Denki-nii feel good in my butt?”
Shinsou groans and kisses you roughly, pushing in the finger. You cry out onto his lips and he starts circling your clit with his other hand again, trying to make you focus on something else.
“Denki-nii will feel so good in here, baby, so warm and tight.”
You bite your lower lip, trying to figure out whether or not it felt right. It’s not like it was painful, but it didn’t feel as good as when your brother’s fingers were in your pussy. It felt strange more than anything.
As he starts fucking in and out of your ass and you start to get used to it, your moans become louder and louder, making Shinsou smile and push in a second finger, “you said you wanted Onii-san’s friends to like you, right? We’ll train this hole and then invite Denki-nii,” Shinsou licks your lips, “Denki-nii will make you feel so good once you’re used to it, yeah? Will you do that? Help Onii-san and his friend?”
You don’t say anything, eyes unfocused as you try to make sense of what your brother’s doing to you, so Shinsou kisses you again before he adds, “can you be a good little sister?”
Your cunt throbs as you nod and nod and nod, “yes, yes, yes, Onii-san I’ll be good, I’ll be good. Can you fuck me now? I promise I’ll be the best little sister to your friends.”
Shinsou smiles and pulls out his fingers to tug at his dick, regaining hardness at the attention. You stare down mesmerized and hungry, biting your lower lip, “I did promise you a reward, yeah? Come on, then.”
Happily you adjust your legs so that you’re hovering over his cock. Shinsou drags it over your folds a few times, laughing when you whine, “Onii-san, I’m so empty, please. I’ve been good, I’ve waited a week, please, please.”
You moan in unison when Shinsou pushes in the fat head, breaching your sensitive and sloppy hole, thighs trembling and shoulders shaking when you finally, finally feel your brother’s cock nestled inside of you, right where he belongs.
Shinsou rolls his hips, slow and sinful as he watches his cock disappear inside of you, praising you for taking him so well, for making him feel so good. You could cry from how he fills you, how his hand knead at your chest through your shirt, thumb and nail grazing over your nipple while his other draws tight circles around your sensitive clit.
“You’re shaking, baby,” he laughs breathlessly as he pumps you full of your favorite cock, and you nod, “’ve been so empty, need more of you Onii-san, more,” you babble, drunk off of your brother’s dick, saying whatever you thoughts come to mind.
He coos and shushes you and thrust in with more purpose. You’re close, and if there’s one thing Shinsou loves, it’s the feeling of your cunt spasming around him when you cum, twitching around his length as he pumps you full of your favorite milk. When you start crying from the over stimulation of his teasing, the wait and the fullness you feel, your brother wipes your tears and puts two fingers in your mouth like you’re a child in need of something to suck on.
You start happily suckling on them, licking between them, moaning when your brother praises you for using your tongue so well. You cum around his cock when Shinsou tells you that you’re such a good girl, that you’re the best little sister in the world, and that you’re so good at understanding your duties as his sister. You feel both your holes twitch in anticipation of how you’ll have cocks in both of them some day. The possibility makes you shudder and drool spills out from around your brother’s fingers.
You’re so relieved and so thankful that your brother does not judge you for having such feelings; that he indulges you in the dirty pleasures that you feel and your wants. He fucks you full of his milk with a declaration of love.
Your greedy little sister pussy is his, but he’s more than willing to share your other holes. It was a happy coincidence that he knows Kaminari likes anal and that the blond is a nasty pervert.
As you catch your breaths, his cock softening inside your pussy, Shinsou reads one message in his private chat with Kaminari as his thumb draws circles onto your hip: I’m so fucking ready holy shit THANK YOU BRO never came so hard in my life