don’t peek (you don’t want to know)
Pairing: Fuyumi x Little sister!Reader
Characters: Fuyumi, Little sister!Reader, Natsuo
Tags/Warnings: tw incest, voyeurism, grinding, pet names, feelings of jealousy and shame and insecurity, tinges of angst
Word count: 1.8k
Author’s note: This was originally sent in as a request! I tweaked it a bit, but nonny if you’re still out there? I hope ya like it ♡
Natsuo Todoroki likes to believe that he has a decent amount of common sense. Sure, he has a bit of a temper- everyone does- but he knows when to keep quiet and when to let it free and he keeps it under a firm rein...most of the time. He knows to pay his bills on time and in full and he knows to check the date when eating food he's had around for a while and he knows to get a good rest before an important test.
Natsuo Todoroki is a reasonable young man with common sense.
That doesn't mean curiosity doesn't take control and cloud his judgment at times, though.
Which is exactly how he ended up like this- mouth hanging open, eyes wide, cheeks flushed, and his cock shamefully hard in his sweats.
He knew better than to peek, of course. Natsuo is well aware of what soft little moans and gasps mean when they come from behind closed door. Natsuo is well aware that his siblings deserve their privacy and that he'd be pissed and humiliated if one of them snuck a glimpse into his room while he was entertaining a friend.
The thing is, though, it's Fuyumi's room the sounds are coming from and Natsuo has never seen Fuyumi with someone, has never heard of her talk about dates or crushes or anything like that. She's never brought anyone home or gone out with anyone other than the same three friends she's had since middle school. Fuyumi doesn't do things with other people- not like he does, at least.
So, of course the noises had his self-control crumbling- especially when he realized how feminine those intriguing little noises sounded from behind the cracked door.
Natsuo has always had his suspicions about Fuyumi, but this?
Well, this is something he would have never expected, would have never dared to think of before.
He had peeked into the room thinking he’d find a girl entangled with his sister and...he did.
He found you in Fuyumi’s bed.
He found his little sister. He found Fuyumi’s little sister.
And he was shocked, of course- things like this don’t really happen (or so he thought) and his family is bent but not this bent.
But in a way it had almost made sense, too. Because Fuyumi never dated and you certainly never dated either and the two of you were so close it was like you could read each others minds half the time. The sisters of the Todoroki clan have always been there for each other and they have always put total faith in the other. Natsuo can’t count how many times he’s seen you crying on Fuyumi’s shoulder and he knows- he’s always known- that you’re Fuyumi’s favorite. You’re the only one that she’ll stand up for when Enji’s on a rampage and he’s seen Fuyumi shove their father away from you when he’s stomped your way with fire in his eyes and his fists clenched. And you always stand up for Fuyumi too- shutting Enji down with cold quips designed to crush the strongest of souls whenever he begins to nag her about children and marriage and being of use to the family. You wipe away her tears and whenever she comes home stressed from work you pamper her with foot rubs and shoulder massages and a manicure and her favorite take out, a bottle of wine.
She loves you and you love her.
Natsuo just didn’t realize how deep that love ran.
And maybe he should have stay shocked. And maybe he should have been horrified. But something had clicked and his wide eyes had softened, his hanging jaw had closed as he watched Fuyumi pull her head out from between your thighs.
When Fuyumi moved, he had caught sight of your pussy- gleaming and wet with your lips spread apart- and then something else had clicked.
His little sister is hot.
Fuyumi is hot.
This is hot.
Oh, god, he’s hard.
And that’s where he is now- cheeks flushed and lashes lowered, one hand over his mouth and the other wrapped around his cock.
He shouldn’t be doing this and he knows that. Natsuo knows that he shouldn’t be jerking off to the way Fuyumi rolls their little sister over and nudges you to straddle her, grind your glistening cunt down against her own.
He knows he shouldn’t, but he does do it- if his sisters can fuck each other then why can’t he get off to it?
A soft mewl sounds and Natsuo has to bite his lip to keep from groaning when Fuyumi chuckles and calls you cute- calls you her sweet little girl.
Shame churns in his stomach, but Natsuo’s cock twitches too- his cheeks burn and his heart races and he nearly cums when you gasp in response, when your hips cant shakily against Fuyumi’s.
Something hot and sick slithers through Natsuo as he watches the two of you and it growls envy as it chases up his guts and wraps around his heart. He doesn’t mean to, but he pictures- just for a moment- what it would be like if you were on top of him instead.
Fucking heaven, probably.
Natsuo’s eyes clench shut and he presses his hand tighter against his mouth as he gasps. His eyes fly open nearly as soon as they close and he panics, darts a terrified gaze back into the room to see if his sisters had heard him.
No, of course not- the two of you are still wrapped up in each other.
Like always.
Natsuo swallows and his gaze lowers in shame, his cheeks simmer with embarrassment.
God, what the fuck is wrong with him? He’s sick. The two of you are sick.
...right?
(Or is that wrong? Because the two of you are only happy when you’re with each other and, fuck, it’s not like the two of you can have kids so maybe it’s...)
Natsuo’s hand falters around his cock and his brow furrows for a moment- something strange swirling through the storm of emotions brewing within him and disrupting the greed and envy and lust and guilt that should feel worse than it does.
“Oh! Oh, baby, that’s it! That’s my good girl!”
“Nee-san!”
Natsuo’s hand circles around his dick again and he lifts his eyes up slowly at the quiet, moaned exchange.
Fuyumi’s hands are on your hips- guiding you as you grind your cunt against your big sister’s, fingers digging into soft flesh and freshly manicured nails scratching against you gently to make you twitch, whimper and whine the cutest little please that Natsuo has ever heard. Guilt and shame and greed and confusion fall away as Natsuo’s cock throbs in his hand and he shudders lightly as he grinds up into his slick palm, feels his heart give a hard thump against his chest as Fuyumi surges up to cup your face and kiss you. It’s hot- hungry and slick and full of soft moans that have Natsuo hiding his own; that have his eyes pricking because he’s never been turned on and torn apart like this before. He’s so close to cumming- so close- and his lashes grow wet when he blinks, his face screws up as his hand twists around his cock and dips down to play with his balls.
Fuyumi falls back against the mattress and her hands fly back onto you- grip tight and cause you to gasp as she urges you to go faster.
“C’mon, baby, please. That’s- that’s it, baby! You’re doing so-”
A moan, an arch of her back and Natsuo can’t help but wonder how he never realized how pretty Fuyumi is when her cheeks are flushed pink and her eyes are sparkling with a hungry desperation.
(It’s probably because he’s never seen her with that look in her eyes before. You were probably the only one who ever has...until Natsuo got nosy.)
“Nee-san, please,” you whine, sweetly, “wanna- I’m-”
“I know, baby, I know. Me too- you’re gonna- gonna make nee-san cum. You wanna make nee-san cum, sweetie? I know- god- I know you can! Such- such a good little sister!”
You nod, a soft sob slipping from you as your hips buck faster against Fuyumi’s, and Natsuo pretends that his head doesn’t dip along just the same as yours, pretends that the thought of Fuyumi asking him the same thing isn’t hot as hell.
(Oh, god- why did he have to peek through the door? Why couldn’t he respect their privacy?)
A whimper sounds and Natsuo can’t tell if it’s from Fuyumi or you, can’t even panic when he groans into his palm over it because, fuck, he’s right there- right on the edge of cumming, right on the edge of ruining his boxers as he watches his sisters gasp and hump against each other.
They’re close and he’s close and he shouldn’t- they shouldn’t- but then-
But then you’re shaking and crying out and Fuyumi is moaning all breathy and hot and her nails are digging into your hips and she’s forcing you to keep humping against her even as your body slumps and you whine out pathetically, gasp whenever her nails sear up your as she begins to cry out.
And Natsuo?
God, he cums in the split second between your orgasm and Fuyumi’s- cheeks wet with overwhelmed tears and burning with blazing heat, vision spotting as his hips pump against his aching fist and his seed spills all over his hand and drips into boxers, smear and ruin the fabric and leaks down to coat his twitching balls as the strongest orgasm he’s ever had rips through him like a hurricane.
Natsuo’s knees almost give out and it’s a miracle that he doesn’t slam into the wall as a wave of dizziness runs through him and he has to stick a hand out against it to keep himself upright.
It takes a moment- two, three, four, actually- for his mind to stop swimming and his high to retreat enough for him to realize that he’s standing in the hallway with his hand down his pants outside of Fuyumi’s door. His eyes dart through the crack in the door, but the two of you are still in your haze- cuddled together and sharing languid kisses, murmuring sweet nothings and smiling at each other with a warmth that has all his shame and guilt rushing back.
...he should have never seen this.
Grimacing, Natsuo pulls his hand from his pants and swipes his palm along the side of his sweats. He looks away from the room- from his two sisters who are nuzzling against each other and looking at one another with a fondness that Natsuo has never been gifted with from anyone- and his teeth clench, his heart twists as he turns on his heel and heads back toward his room.
He’s an idiot. They are, too. None of this should have never happened. The two of you should have never happened either.
But Natsuo doesn’t do anything about it- only walks back to his room and lays down in bed. He doesn’t confront Fuyumi. He doesn’t confront you. He doesn’t confront himself.
Natsuo lays there with his cum crusting on his sweats and he wonders...
...why not him?
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