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Deku has always been the curious sort…dangerously so… especially when it concerns his two hyperfixations: Quirks and Kacchan. He realizes that his interest in his hero partner far surpasses what would be considered “conventional” by societal standards and for many years it caused a conflict between them. But with age and experience, Deku has become a little better at hiding certain proclivities and dark thought patterns concerning Katsuki. It’s taken him years to build and manipulate their relationship into something that gives him greater access to the other hero. Katsuki has high fucking walls and Deku has had to fake some major shit in order to be granted coveted keys to the kingdom. He could even call them “friends” now, but it’s not enough. He craves more, NEEDS unfettered access to all of Katsuki. He can’t explain his obsession. It’s always just been a part of him since they were childhood friends. There’s always been this unbearable itch under his skin to hurt Katsuki. He doesn’t want to maim him or truly injure him of course, but he wants Katsuki to beg for it…beg Deku to be the one to dole it out. Deku wants to be the god in Katsuki’s universe, the one to control his pain, his pleasure, his desires, his needs. But Katsuki is stubborn and prideful, keeping Deku carefully at arms reach and frustrating him to no end.
For years, the need has set festering and when the solution practically drops into Deku’s lap, he palms his face and scolds himself for not thinking of it sooner. How did it NEVER occur to him to combine his interests like this… He could have fixed his little problem years ago. Of course he arrested the villain distributing the quirked powder illegally on the streets, but not before he confiscated a large quantity of the substance for his personal stash that he keeps in a vault at home. He collects them, you see, rare and unusual quirked products with a broad range of uses and effects. You never know when you just might need them. Once the producer is arrested, they disappear off to Tartarus never to be seen again. While Deku understands the concept of punishing them for their crimes, he can’t help but think that it’s a colossal waste of quirk potential. In this case, he just couldn’t look past the perfect solution to all of his problems.
Deku resists the urge to smirk when he knocks on Katsuki’s office door and his partner is already squirming and looking flushed at his desk. Sweat is dampening the strands of his shaggy blonde hair, making the typical spikes droop and plaster to his forehead while his cheeks are glowing red with heat. Katsuki shifts over his seat and Deku licks his lips as hazy red eyes glare up at him. “What’s up, Deku?” he grunts, lacking his normal bark.
Deku glances at the empty coffee cup on Katsuki’s desk, pleased to see that all of it is gone. He’d used the entire packet of quirk powder as he’d mixed Katsuki’s morning coffee and hand delivered it to his desk just like he does every morning. “Just checking in on you,” Deku purrs, striding into the office. “You get the reports from yesterday’s arrests submitted?”
Katsuki gives an affirmative grunt and wiggles in his chair. Deku silently wonders if he’s soaked through his boxers yet. The quirk has a longer activation period. So right about now, Katsuki should be feeling intense arousal. He doubts that Katsuki has even taken the opportunity to try and “relieve” himself yet. However, he’ll be in for a rude surprise when it doesn’t work the way he probably thinks it will. “Kacchan, are you feeling alright? You look a little flushed,” Deku goads when Katsuki fumbles with his pen and gives a low groan as he bends down behind the desk to pick it up.
“‘M fine, nerd,” he growls defensively, but Deku almost laughs at the quiet whimper that follows the words. Katsuki’s eyes widen at the sound as if he can’t believe that he’s the one that made it. His eyes dart to Deku and narrow. “I’m busy, so go find someone else to bother,” he snarls, clearly trying to get Deku to vacate the space immediately. Deku bites his lip to keep his laugh contained.
“Sure, Kacchan!” he chirps easily. “Let me know if you need any help with anything!” Deku turns and walks slowly from the office, making sure to close the door on his way out before hustling back to his own office to pull up the hidden camera feeds on his laptop. He’s just in time to watch as Katsuki hurriedly unzips his pants and thrusts his hand down into his boxers now that he’s alone. Deku can’t hear anything through the cameras but he can see the rapid rise and fall of Katsuki’s chest and his hand frantically moving between his spread legs just below the edge of the desk. For over an hour, Deku is riveted, watching Katsuki’s skin turn a deeper shade of red and the sweat drips down his face as he tries and fails to get himself off. He wonders if Katsuki has soaked through his uniform yet, imagines the juicy sounds of that wet little cunt as his partner finger fucks himself almost hatefully in his desperation. Katsuki looks delirious, rolling his head over his shoulders, eyes closed and trembling so hard that he acts like an exorcism is being performed. He looks transcendent in his suffering. Deku gets lost in it, reaching down between his own legs to palm his throbbing cock through the fabric of his trousers.
Katsuki is supposed to be on patrol in twenty minutes, but Deku has already made arrangements to have it covered by another hero. There’s perks to the two of them running the agency together, allowing Deku to arrange the dominoes just for this auspicious occasion. Their offices are the only two on this floor and the moment he dosed Katsuki’s coffee, he’d sent out a memo that they weren’t to be disturbed under any circumstances for a supposed “Top Secret Mission” briefing that would take up the entirety of the day. He imagines things are about to get very noisy and he’ll be goddamned if anyone else sees or hears his Kacchan like this. No… this is for Deku’s eyes only.
His lips curl up into a wicked grin when Katsuki suddenly curls in on himself, shaking and gripping the desk. Deku’s eyes widen when little crackles of Katsuki’s quirk light up the screen as they pop and sparkle against the desk, scorching the wood. His partner has immaculate control of his quirk, so the sight of Katsuki losing it is fascinating. A muffled sob can be heard through the shared wall and Deku’s cock kicks at the haunting sound. He’s almost ready.
After a few moments, Katsuki tries and fails to stand over wobbly legs before collapsing back into the chair, making it roll back just enough to see. Katsuki’s pants aren’t even on anymore, laying in a rumpled pile under the desk next to boots that had been kicked off at some point. Clearly lost in agony, Katsuki spreads his legs wide, no longer trying to hide beneath the shield of the desk and Deku licks his lips at the high definition view of chubby slick-shined pussy lips. He taps his fingers on the mouse, zooming in as Katsuki’s fingers begin desperately rubbing over a swollen red clit that looks nearly painful under Katsuki’s useless ministrations.
Katsuki’s face tilts back and up towards the camera, sweaty hair clinging to his forehead and his usually immaculate eyeliner running in macabre streaks down his cheeks as more muted sobs pour from between pink lips. The darkness in Deku stretches and grins with anticipation as he adjusts his aching cock in his pants and stands.
By the time Deku reaches Katsuki’s closed door, he can hear the pained and frustrated groans from within. He carefully schools his vicious smile and cracks the door open. “Kacchan, are you alright–?”
“Fuck!” Katsuki screams and Deku is just in time to see his obsession flail about at being interrupted as Katsuki tries to hurriedly cover himself. “DEKU! GET OUT!”
“Kacchan, I could hear you through the wall. Is everything okay?” Deku purrs with mock concern, quickly striding forward closer to the desk after shutting the door and subtly clicking the lock in place. Katsuki’s eyes are wide with horror as he tries and fails to scooch closer to the desk while cupping over his bare dripping mound.
“Fine, Deku! Just got hit with a quirk or somethin’! Now, get out!” Katsuki snarls through gritted teeth, but the defensive words lose effect when they’re followed by a low tortured groan.
“Kacchan, have you tried–”
“Deku, I swear to god, I am not having this conversation with you right now!” Katsuki hisses, lashes fluttering in agony. He squirms in his chair and Deku can’t help dragging his tongue over his bottom lip at the lewd sight.
“Looks like a nasty sex quirk, Kacchan,” he murmurs in a low voice, letting his mask slip just a little bit. “Who knows what the effects might be. Maybe we should call the Quirk Containment Unit…” He lets the sentence trail off.
“NO!” Katsuki screams, his pride kicking in just as Deku knew it would. “You’re not fucking locking me up so the nerds can poke and prod me like a science project. I just gotta–” he whimpers and Deku’s eyes widen as he watches Katsuki try to subtly stimulate himself.
“You think it’ll help?” Deku asks calmly, cheek twitching with hidden amusement.
“It’s gotta… I just can’t seem to…” Katsuki groans again, the sound stuttered and animalistic. Deku doesn’t hesitate to use the opportunity to round the desk and close the proximity between them. Katsuki seems to forget all about his audience as he tips his head back and his legs spread while he starts to rub once more at his swollen clit. “It’s right fucking there,” he whispers hoarsely.
Deku braces a hand on the back of Katsuki’s chair and turns it to face him. Katsuki’s eyes stay closed, features scrunched in intense concentration while his fingers move frantically between his legs. Wetness soaks the leather of the chair and coats the insides of his thighs, slick sounds mixing with Katsuki’s heaving breaths. His whole body tenses as if he’s right on the cusp of cumming his fucking brains out, but Deku secretly smirks knowing that relief is not going to come. Katsuki’s jaw pops with how hard he’s clenching it and his fingers move even faster over his wet sloppy folds. After several long moments, a broken sob makes Deku choke back a victorious laugh. “Fuck! I can’t!” He screams in frustration. “What the fuck?!”
Deku practically vibrates with giddiness when Katsuki’s dilated eyes crack open and widen as if he’d completely forgotten that Deku was even there. Crystal tears pour down his cheeks, making his face muddy with eyeliner. He looks so deliciously broken and desperate that Deku can’t contain his patience any longer. “Does Kacchan want some help?” he growls in a low tone while bracing his hands on either side of the chair just over Katsuki’s shoulders and leaning in close.
If possible, Katsuki’s face turns even redder and his features contort into rage. Deku can already sense the argument coming and just as flushed lips part, blackwhip flies out behind him and a singular tendril darts into Katsuki’s mouth before he can even utter a word of protest. Katsuki jerks back in surprise, his hands flying upwards and leaving his pretty pussy exposed. Pops of light spark from his palms, but before he can do any real damage, blackwhip wraps around each wrist and yanks them back to the armrests of the chair. Katsuki’s glare turns deadly but Deku gives him a serious look. “Kacchan, it’s only going to get worse unless you let me help,” he rumbles over the sound of Katsuki’s muffled yells of outrage.
Katsuki practically vibrates in place with his fury and coerced arousal, but Deku ignores him to reach down and swing. The slap rings loudly in the office and Katsuki jolts in the chair from the harsh impact, slick flying outwards around Deku’s palm as he strikes the puffy folds of Katsuki’s pussy. Katsuki’s legs try to fly closed, but blackwhip lashes out and wraps around his ankles to yank them even wider apart. Deku licks his lips and meets Katsuki’s watery glare as he swings again harder. Katsuki flinches from the slap, but then a long garbled groan follows. “See, Kacchan,” Deku purrs, struggling to keep his darker impulses from showing too soon. “Maybe you’re just going about this the wrong way. Let’s try something new, ok?” Slap! Katsuki’s moan this time is long and loud even through his stuffed mouth, ruby eyes rolling upward.
“Does that feel good?” Deku growls, striking again, watching Katsuki’s features contort with pleasure. His next slap is even harder and Katsuki quakes and his lashes flutter. His moans are tortured and pleading through the tendril spreading his lips wide. Deku can’t look away as he pushes the tendril deeper into Katsuki’s mouth. Katsuki gags as it touches the back of his throat and Deku grins when pretty eyes slam shut while his chest heaves when the thick tendril pushes further past his tonsils. He swings again, slapping hard over sloppy reddening folds, making sure to impact the juicy swollen nub of Katsuki’s clit. Katsuki chokes on the girth stretching open his throat and his body shakes so hard that Deku briefly worries that the chair may not hold. Little pops of Katsuki’s quirk scorch the chair arms, making Deku grin.
“Do you need to cum, Kacchan?” Deku coos, stroking the tendril in out of Katsuki’s mouth without actually leaving his throat. His cock kicks at the lewd sounds of gagging and he palms Katsuki’s messy folds for a moment, fascinated by the bulge in Katsuki’s throat. “I bet I can make this stubborn cunt squirt for me,” he then teases, driving two fingers into Katsuki’s tight hole. Katsuki gurgles a sound as Deku pulls back blackwhip just enough for Katsuki to suck in a snotty breath through his nose. He pumps his fingers a few times, but chuckles when Katsuki’s eyes fly open the second they retreat. Katsuki’s glare is long gone and replaced by something hazy and desperate. Tears track down his cheeks and he mumbles something around the tendril in his mouth.
Deku reaches for the lever of the chair and yanks on it, Katsuki’s eyes going wide with surprise as the back suddenly reclines. Black whip wraps around the chair to stabilize it while Katsuki’s legs are bent and pulled up from the floor until his ankles are in the air and spread wide. Deku maneuvers himself easily between them and takes a moment to admire the view as Katsuki squirms and sobs. The new position puts Katsuki’s pussy just over the edge of the chair seat, completely at Deku’s mercy. The sound of gagging gets louder as Deku speeds the thrusts into Katsuki’s throat, making him gurgle as it dives deep. He cracks his hand down hard and fast, the chair creaking with how hard Katsuki jolts. “Bet I can make you cum just from spanking this slutty pussy,” Deku purrs as he slaps the bright red folds again. “Should we find out, Kacchan?” Katsuki gurgles a helpless sound and quakes beneath blackwhip’s tendrils. Deku’s smile creeps across his face as he finally unleashes some of the violence that he’s been so careful to keep concealed. Katsuki wails as the tendril in his mouth pulls free just as Deku allows his quirk to flow through him. He slaps Katsuki with quick measured strikes only milliseconds apart while Katsuki screams to the ceiling above him. It takes only a minute before Katsuki starts to rattle in his bindings and fluid begins to spray from him like a hose, dousing Deku’s hand. Deku only hardens his spanking and Katsuki’s sounds grow high-pitched. “That’s it! Get it all out, Kacchan!” he coaches in a chipper voice as Katsuki completely soaks him with his release.
“Deku, please!” Katsuki finally screams raggedly, begging for mercy. Reluctantly, Deku stops his strikes and soothes over bright red folds with the flat of his hand. Katsuki whimpers at the touch, face completely ruined with black tear streaks and spit. His breath saws in and out of his lungs in gasping inhales as if he just finished the hardest villain battle of his career. “Holy shit…” Katsuki mutters breathlessly, sounding relieved. Deku almost lets his smirk show. This quirk isn’t done yet, it’s only just getting started.
“Feel better, Kacchan?” Deku asks, trying to smother the sly tone itching to creep out.
“Fuck,” Katsuki grunts, but then seems to choke on air. His teeth clench together and he groans. “It’s still fucking there,” he rasps, watery eyes darting up to meet Deku’s before glancing down at his restraints. “Deku, what the fuck was all that?” he hurries to ask, even as his body once more begins to tremble and the redness returns to his cheeks.
“Just helping Kacchan through this quirk,” Deku chirps readily.
Katsuki’s breaths pick up once more. “How the fuck d’you know what to do?” he slurs, squirming in blackwhip.
“Lucky guess,” Deku replies in a low purr. “Did you like it?”
Instead of answering, Katsuki makes a pitchy whine and bows against the chair. “It’s still fuckin there,” he croaks, sounding panicked.
Boldly, Deku dips three of his soaked fingers into Katsuki’s tight little hole, forcing it to stretch to accommodate him. “Don’t worry, Kacchan. I won’t leave you like this,” Deku murmurs, eyes fixated on Katsuki’s as he starts to pump his fingers slow and deep. Katsuki sucks in a sharp breath, eyes narrowing as he opens his mouth to no doubt protest with his insufferable pride. Blackwhip shoots into the open hole, cutting off anything that Katsuki was about to say with a lurching gag as it dives back into Katsuki’s esophagus and stays there. Katsuki’s eyes close, cutting off their connection. “I know what you’re going to say, but you need this, Kacchan,” Deku explains calmly, even as his excitement scorches his veins. His cock jerks and leaks, still trapped in his pants as he abruptly pulls his fingers out to add a fourth, shoving them all back into Katsuki’s slick hole with force. Katsuki jerks from the stretch, unable to cry out with his mouth stuffed full. “This slutty fucking body is begging for attention and you’ll just be torturing yourself without help. I can give you what you need, Kacchan.”
Without removing his fingers or slowing their task, he reaches with his free hand into his pocket and pulls out the bottle of lube he had stashed there. Katsuki’s eyes are still clenched tightly closed as he struggles to pull in a breath when the tendril in his throat begins to move once more. Deku takes the opportunity to douse Katsuki’s pussy in the slick substance, making sure that it drips down over Katsuki’s tight little pucker below and drips to the leather seat. One of blackwhip’s tendrils shoots forward and kisses Katsuki’s tight furl and begins to rub over it, smearing the lube. At just the light touch Katsuki’s eyes shoot open, wide and panicked, making Deku lose composure on his grin. “Have you figured it out yet, Kacchan?” he purrs wickedly when the tendril begins to push into the too tight entrance while he fingers Katsuki’s clenching pussy. Katsuki gurgles a helpless sound and begins to squirm as the tendril pushes deeper into his underprepared ass. Deku hardens his thrusts, curling his fingers hard and fast so that slick flies outwards. Katsuki begins to rattle so hard that the chair creaks under the strain. The tendril in his throat yanks free so that he can pull in a gulping breath, only to strike back in and make him choke on a gag. Sweat drips down his hairline to mix with the tears running down his ruddy cheeks while spit runs down over his chin. “Look at you,” Deku coos. “Your face is just as messy as this drooling cunt.” One of Deku’s tendrils lashes out and whips at Katsuki’s asscheek, the sound cracking the air amongst Katsuki’s gagging wet gurgles.
He can feel Katsuki clenching down hard over his fingers as the tendril in his ass slithers deeper. “The trick is pain, Kacchan,” Deku growls after a few moments, dragging the tendril out of Katsuki’s ass slowly, teasingly. “Gotta make you really feel it…” He allows Katsuki to suck in another snotty breath as the tendril in his mouth retreats to his tongue. Katsuki’s eyes are hazy and watery when they land on him and Deku can practically feel the desperation radiating from his partner, can taste the pure NEED calling him to action. He whips another tendril against Katsuki’s ass and this time he can hear the muffled cry, making his cock kick violently against his zipper.
Katsuki’s pussy is soaking the seat and drenching Deku’s hand as he crooks the last finger in with the others. Katsuki’s breaths come harsh and fast, dilated pupils landing on Deku with something close to fear, but Deku ignores him in favor of watching as he begins to push his hand past fleshy resistance. The tendril at Katsuki’s ass and the one at his throat thicken simultaneously in preparation. Katsuki’s whine is high pitched and pained as Deku puts more force behind his arm and his fist sinks into the warm cavern of his cunt. Katsuki’s eyes slam closed and his cry vibrates around the tendril in his mouth just as his pussy spays. Deku doesn’t hesitate to pull his fist free and punch it back in with more force, making Katsuki writhe as more of his release bursts from him like a broken hydrant. Deku is ruthless as he begins pumping his fist within Katsuki’s womb while the two tendrils shove deep into Katsuki’s other holes. Katsuki arches with a desperate choke as he’s stuffed all at once. His pussy quivers and sucks around Deku’s hand as he fist fucks Katsuki. “There’s a good little puppet,” Deku snarls, a vicious laugh bubbling in his throat. God the sight alone is almost enough to make Deku come in his pants. “Keep cumming for me just like this.”
Even when Katsuki sags against the seat and tears pour down his face, Deku is persistent. Another tendril flies to Katsuki’s ass and twists through the still dripping mixture of Katsuki’s release and leftover lube before wiggling in next to the thrusting tendril already buried. Katsuki jerks but is unable to make a sound as the tendril in his throat continues thrusting. All he can do is try to suck in short breaths to alleviate his lungs when he can. Deku feels high as he undoes his pants one handed and pulls out his heavy aching cock. It’s not quite as thick as his fist but is damn near. Deku can feel it as his fist punches against the barrier to Katsuki’s womb, he’s so tempted to just punch it out, but then again…Why do that when he can just fuck it open with his cock. The idea is so appealing that he yanks his fist out with a wet squelch and lines up his cock with the gaping hole. His cock might not be as thick, but his length will be perfect to break that barrier open. He rubs the thick head through the mess of Katsuki’s folds. “Are you ready, Kacchan? I’ve always wanted to stuff your cunt, break it open and breed you properly. Are you excited?” Deku crows and rams his cock into wet clinging walls. It’s a little loose, but that’s to be expected after fisting him open. “Let’s tighten this slutty little cunt up, hmmm…” Another tendril of black whip worms its way into Katsuki’s ass, putting pressure through the vaginal wall and making Katsuki tighten up until he’s clenching Deku’s cock with an iron grip. “There we go…Nice and fucking tight again,” Deku murmurs, beyond pleased with himself. He rocks his cock shallowly with a few exploratory thrusts while Katsuki gurgles more helpless whines, his eyes rolling up and lashes dripping with tears. Deku pulls back the tendril in his mouth until it’s out of his throat and Katsuki can suck in a deep breath through his nose. He can see where Katsuki’s teeth are grinding into the tendril with a clenched jaw. Deku smirks as he thickens the tendril stuffing his mouth, making it widen absurdly and no sound can escape.
Green lightning dances over Deku’s skin as the thrusts into Katsuki’s ass delve deeper into his intestines. He funnels his quirk to his cock as he grinds deep into Katsuki’s pussy, he’s only halfway in when he meets the wall of Katsuki’s cervix. With one flick of his quirked hips, he drives forward and breaks the little barrier open. Katsuki’s eyes fly wide open and sightless, his scream gurgling even over the thickened tendril blocking his mouth. Warm liquid bathes Deku’s front with Katsuki’s release, but he doesn’t stop. He starts pistoning his hips, eyes rolling back at the feeling of Katsuki’s tight velvet walls stroking his cock. The feeling of blackwhip thrusting and squirming in Katsuki’s ass only adds extra sensation to the entire experience and Deku doesn’t know if he can ever go back to regular sex again after this. Katsuki thrashes and squirms in the chair, eyes rolling up lewdly as Deku pounds into him mercilessly, green lightning flashing all around him. “No one can give you this, but me,” Deku finds himself hissing through clenched teeth as his balls start to draw up tight.
He’s getting close so he extends another tendril of blackwhip to strike at Katsuki’s ass with welting stripes, while another curls up and whips at Katsuki’s clit. The tendrils in his ass thicken and dive so deep that Katsuki’s flat belly jumps outwards in a lewd bulge. The one in his mouth starts twisting and curling in his used throat, making his chest heave with aborted gags. Deku feels high watching an overwhelmed Katsuki fight it all, palms sparking brightly against the chair’s armrests, even as his pussy begins to wildly spray around Deku’s cock. “Yes! That’s it, Kacchan!” Deku praises, sounding feral and unhinged as his own release slams into him and he grinds deep into convulsing pussy walls. His cock kicks heavily as his balls unload what feels like a flood of cum that he’s been saving up for this very moment. “Fuck yeah,” he grunts. “Always wanted to cream your tight cunt…”
Deku is still twitching with aftershocks when Katsuki suddenly falls limp against the chair, eyes fluttering closed, making Deku smile as he withdraws blackwhip entirely. Katsuki doesn’t move as he pulls his messy cock free and examines the carnage left behind. Bright red welts are hashed across Katsuki’s ass cheeks. His little clit and folds are bright red and swollen with abuse. His cheeks are a mess of black eyeliner and spit. His used holes are gaping open and a steady flow of Deku’s cum is dripping from his cunt. His breaths are still heavy, but he doesn’t move an inch from his crumpled heap in the chair. Deku’s smile is wicked as he pulls his phone from his pocket and snaps several photos for himself. He’s so tempted to leave Katsuki like this, but that would ruin any future chance of this happening again.
The process is painstaking as Deku picks Katsuki up and carries him to the locker room down the hall. He cleans him up meticulously and re-dresses him before pulling the syringe from his pocket, a special little cocktail of combined quirks that he injects directly into Katsuki’s neck. When Katsuki wakes up slumped over his desk, all of Deku’s marks will be healed and he’ll have no memory of the last two hours. He’ll simply think that he fell asleep at his desk. Deku thinks he’ll make this a weekly thing from now on. He has so many things he wants to try.
After all, what’s a little pain between friends?