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[NSFW] FIC - "Five Things Katsuki and Izuku Did That They Don't Know Their Friends Know About"
🕑 Added 2025-08-14 17:00:00 +0000 UTCBKDK | post-canon | getting together | humor
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Five Things Katsuki and Izuku Did That They Don't Know Their Friends Know About
01. Several days into investigating a lead on a villain, they agree to meet up with Kirishima and Kaminari in a nearby tourist town where the two are chasing their own leads. It wouldn’t hurt to exchange whatever information they’ve gathered so far.
They find a dim booth in a busy little izakaya, where Kaminari and Izuku spend most of the evening turning varying shades of red every time they glimpse the building across the street. No signs indicate its name or purpose, but the traditional doors are painted with elegant plum blossoms, and twin paper lanterns glow red at either side of the entrance.
Through the thin bamboo slats of windows, they glimpse bare shoulders and glossy red lips. Faint trills of feminine laughter and the chords of a shamisen filter into the quiet night.
Later, at an inn, Kirishima asks if he wants to join them for a drink. Katsuki sneers and announces he’s heading to bed. He’s meant to be sharing the room with Izuku, but Izuku must have gone out with the others. He doesn’t think much about it until Izuku returns two hours later, alone, and stinking of perfume and tobacco.
Katsuki, still awake mulling over their next move tomorrow, sits bolt upright in his tiny twin size bed. “You reek,” he says.
The accusation in his tone catches even himself off guard. Izuku’s face burns, and Katsuki suddenly can’t breathe.
“I was going to shower,” Izuku mumbles as he bends over his bag to rummage for a change of clothes.
Katsuki’s palms grow sweaty. His stomach knots, and his chest wrenches. He’s going to throw up.
Instead, with a remarkable calm that he acquired during the war, he says, “You know you can’t put down sex as a business expense, right?”
Izuku has the nerve to sputter and turn an even deeper shade of crimson. “I didn’t... d-do anything... like that. We just talked. They tell great stories!”
Eyes narrowed, Katsuki says, “You guys went to a brothel and talked ?” Somehow, with Izuku, it doesn’t seem so unlikely.
Hugging his change of clothes to his stomach, Izuku nods. “Well, I can’t speak for Kaminari-kun or Kirishima-kun, because I left first but yeah. Lots of people pass through here, and they tell the women just about everything, so they’ve got a lot of great stories. I-I was actually going to suggest we go back together tomorrow. They might know something.”
His pulse slows with every word Izuku speaks, until he has the mental capacity to admit it’s a pretty good idea.
The next evening, after parting ways with their friends, Izuku leads Katsuki to the brothel. He rolls his eyes at the way Izuku very obviously averts his gaze from all the tits practically spilling out of loose, floral-print kimonos, as if they don’t work with heroes of all genders every day dressed in skin-tight costumes that leave nothing to the imagination.
But he can’t shake the kernel of jealousy that lodges behind his ribs. He deals with it by being all business and no nonsense, even when two women steal Izuku away with muffled giggles and knowing glances at Katsuki.
He trusts what Izuku said last night about not doing anything with them. Still, his patience with the nerd’s absence lasts all of ten minutes before he gives up on questioning the owner and stalks through scented salons and dimmed corridors to find Izuku.
The last thing he expects is to walk in on the women teaching Izuku how to deepthroat a banana. Izuku’s eyes go comically huge. He instantly chokes around the condom-covered fruit jammed into his mouth while Katsuki’s entire body erupts in an explosion of sparks.
02. They don’t talk about it. But at night, Katsuki lies awake and remembers Izuku’s pink lips stretched obscenely around latex, shiny with spit and lube. He presses a hot palm to his cock, moaning into the back of his hand.
After two weeks of this, Katsuki reaches his limit. When he enters the kitchen, he spots Izuku at the counter, innocently (or not, Katsuki doesn’t even know anymore) handling a cucumber as Kaminari cuts a second one into slices, and he goes lightheaded with how quickly blood redirects to his dick.
Unfortunately, Izuku notices. He drops the cucumber, face flaming, and Katsuki turns on his heel, marching back into the common area because fuck this. He takes the stairs up to Izuku’s floor, lets himself into the nerd’s room (he rarely locks it), and waits.
When Izuku finds Katsuki lounging on his bed a half hour later, he lets out a high-pitched “eep” and frantically looks around as if there was even a chance he’d entered the wrong room. Dork.
“Kacchan,” he begins, but Katsuki has to catch him off guard or else the nerd will come up with some irritating lie that will just piss him off.
“You still practicing on fruit?” he asks bluntly, ignoring the way his ears burn.
“I-I don’t know what you—that is, it was just the one, uh, I haven’t—”
“Don’t even think about running away, Izuku,” Katsuki growls, because the nerd is creeping backward toward the door. “We’re fucking talking about this. You were supposed to be questioning them, and instead, I find you with a banana down your throat.”
“Oh my god, Kacchan,” Izuku wails, covering his face with both hands. “I’m sorry, I was just curious, and who else would know how to do it better than a sex worker?!”
“Why the fuck would you need to know how to do that? Whose dick are you planning to suck?!” Katsuki demanded, jumping to his feet in a sudden fury.
Izuku wouldn’t meet his eyes. “Why are you even asking me that? What does it matter?”
“Because it does!” Katsuki shouts, which he’s well aware explains nothing at all, and Izuku says as much.
Neither of them hold back in the ensuing argument, during which words like ‘blowjob’ and ‘choke on a cock’ are exchanged, and they're so heated that they forget just how thin the dorm walls are.
It only ends when Katsuki demands, “Then practice with me!”
He goes white as a sheet when he realizes what he’s said, but he’s never once gone back on his words so he stares Izuku down in the heavy silence. When Izuku only blinks owlishly at him, mouth agape, Katsuki scoffs and shoves past him.
03. A few days later, Katsuki wakes from a deep sleep to the feeling of someone climbing onto his bed. He’s immediately alert, palms sparking and adrenaline surging. Then he catches the subtle airy scent of a familiar deodorant, and he raises his hands—for light rather than an attack.
Izuku is on all fours at the foot of his bed, looking terribly sheepish. “H-Hi, Kacchan.”
Katsuki scowls and closes his fists, dousing them in shadows. “Go on then. Can’t fucking wait to hear why you’re sneaking into my room in the middle of the night.”
The darkness must lend Izuku courage because his voice is low and barely trembles when he replies. “Let me show you.”
Neither of them say anything else as Izuku crouches between his legs, peering up at him with huge eyes that beg permission. In answer, Katsuki swallows hard and lifts his hips like an invitation.
Izuku inhales sharply through his nose. Then he reaches for the waist of Katsuki’s pajama bottoms before unceremoniously shoving his face into the crease of skin between Katsuki’s groin and thigh.
Muttering a curse, Katsuki grips the sheets, watches as Izuku tugs down his pants and boxers, baring his half-hard dick to Izuku’s hungry gaze.
“Izuku,” he begins in a whisper that dies the moment something warm and wet licks up the base of his shaft. “Fuck.”
“Is this okay?” he asks, lips hovering above the damp tip. He prods his tongue against the sensitive slit.
Katsuki’s hips jerk. “Yes, shit, what the hell? You snuck in here just to suck me off, you pervert?”
“You said I could,” he says with a note of defensiveness. Before Katsuki can address that, though, Izuku continues. “I want to. I’ve been wanting to. Been thinking about this for ages.”
Then, slick tight heat closes around his length, and Katsuki’s head falls back onto his pillow as he moans. This might be the first time anyone’s touched his dick, but he feels pretty confident that the damned nerd took the deepthroating lessons to heart.
Izuku releases his cock just long enough to murmur, “Shh, Kacchan, we have to be quiet,” but doesn’t wait before swallowing him back down again.
He is not, in fact, quiet.
04. A cave isn't ideal for their first time, but Izuku isn't complaining so Katsuki's not about to stop. In fact, Izuku is doing the opposite, holding up his thighs, legs open and obscene, breathless and impatient. Katsuki grips tight around the base of his dick to keep from coming on the spot.
"Hurry up, Kacchan," Izuku pants, more bossy than whiny. "Hurry before they get back. Come on. Please, please, please–"
Katsuki kisses him to shut him up. Then he's pressing in, and his thoughts go dark and fuzzy. Izuku clings to his shoulders, his arms, hips bucking, legs urging him deeper and faster. The cave echoes with their gasps and moans, and Izuku's breathy mantra of, "Right there, right there, there there there, don't stop–"
Neither of them hear the stifled sound of surprise at the mouth of the cave followed by the shuffle of footsteps and a barely audible hiss of, "What the fuck, guys?"
05. After several rounds of shogi and drinks, when their friends are passed out on futon mats and scattered game pieces, Izuku drapes himself over Katsuki's chest. They haven't shared their relationship with the others yet, but the looks they've been getting means it won't be long now.
Izuku smiles dopily up at him and plants a sloppy kiss to his jaw. Then he promptly falls asleep with Katsuki's heartbeat beneath his ear. Katsuki doesn’t kick him off until at least an hour before dawn.
~fin
