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The sea is alive with rolling tides and roaring waves crashing against the small sailboat Izuku is settled on, swaying and bobbing with the gnash of gentle and harsh waves pushing against it.
Izuku knows the ocean is a brutal, desolate place of kill or be killed.
And Izuku is witnessing it first-hand.
A shark mer, smaller than Kacchan - everyone is smaller than Kacchan - had tried to intimidate the large mer when he was showing off for Izuku, allowing the man to touch his smooth but tough hide and glide his hands across his fin that sliced through the water. Izuku would forever be fascinated by Kacchan - from the way his gills shifted and breathed to his sharp, jagged fin tip brutalized from years of fighting for his territory and winning. Izuku knows Kacchan was territorial - it came as a default because not only was this Kacchan but shark mers were exceptionally territorial around mates and territory.
And this was Kacchan's territory, clear by the markers of scent and dried blood Kacchan had told him he used to mark his territory.
At that point, Kacchan had told him, it was hard not to see the territory was owned by a very powerful shark. Either this mer didn't think to check any possible territory markers, or it swam in with the intention of claiming the territory as its own.
Izuku didn't wait to say the mer had it coming but...
The sight in front of him... it's a brutal, ruthless sight.
Kacchan had gone under not long after sensing the shark mer circling Izuku's boat, that tipped fin slicing through the harsh, rippling waves like a knife through smooth, warm butter. He could hear, feel, see the collision between the two mers. It wasn't hard not to be drawn to the sounds of fins and tails slicing through the water and slapping against the surface as they wrestled. Izuku knew Kacchan was winning even though it was hard to figure out who was who. Their tails were the same shade of light grey, but Izuku could barely see the tail scars on Kacchan's much bigger tail as he dragged the shark mer far away from the surface.
Izuku couldn't see much - it was hard to from how dark the ocean was and the blood rapidly tinting it a maroon red - but Izuku could see the way Kacchan's body thrashed and disrupted the waves of the ocean, creating his own with his body. The torrent of waves crashed and knocked into the hull of Izuku's boat, making his body rock as he stared at the frothing water atop the mer's fighting bodies. It was clear to Izuku that Kacchan showed the mer no mercy as the smaller mer tugged and grasped uselessly at the air when their hands breached the surface, head breaching for a split second to scream in agony.
Izuku didn't know what it felt like to be torn apart alive while your guts spill and your heart thunders away in your split open chest cavity, but from the noise the shark mer was making, it didn't seem pleasant.
Izuku could see the shredded organs and skin chunks float in the water as Kacchan tugged the mer into the overwhelmingly silent depths with quick, powerful movements, the sunlight barely penetrating the swirling waves and engulfing darkness sitting below Izuku, who continued to bob up and down on his little sailboat. He knew what would become of this shark who made a frankly stupid decision, but he was scared for of Kacchan.
Izuku knew this was a sick sight, something that would simply burn itself into his eyelids and stay there, but he couldn't look away. He couldn't look away at how he could see glimpses of Kacchan's body thrashing and pulling at the mer's body, shredding it, and cracking its chest cavity open with the sheer power the mer held.
Izuku... Izuku knew Kacchan was scary, but this was a whole new high.
Izuku leaned closer, arms wrapping around the metal railing of his little sailboat to anchor himself, staring at the blood-red ocean water staining the edges of his boat as stained red sea foam clung to the sides of Izuku's boat. "Kacchan..." Izuku whispered, a sound washed away by the salty sea air as he watches the bubbles - from the mer screaming for its useless life - ceased, nothing but the salty seafoam cresting the waves and chunks of bitten and torn-apart mer floating on the cold, quiet surface.
Then, Kacchan emerged. His body crested along a wave as his fin sliced through the blood-red waves, circling Izuku's stationary boat as Izuku scrambled away from the deck of the boat. Izuku's wet feet slapped across the board ship top, rushing over to the edge of his boat where it dipped down, perfect for interacting with Kacchan.
"Kacchan! Ka-Kacchan," Izuku huffed as he settled down, staring at the shark mer who floated straight up in the water, hiding just under the surface, those piercing carmine eyes staring at Izuku through the rippling waves. "Are you okay?" Izuku whispered, braving the fear flowing through his body as he dipped his hand into the water, reaching down as his other hand locked around the edge of his boat. He was scared of what him falling into the water would do, fearful of activating Kacchan's predatory instincts to a creature thrashing in the water. Kacchan stared at his hand for a moment, his body lurching upward the last two inches as his skin - almost inhumanly smooth - slid across Izuku's hand, allowing Izuku to cradle his face. "You... You aren't hurt, are you?" Izuku whispered, trying to hold back tears. He was scared... terrified even, but he knew Kacchan wouldn't hurt him. Kacchan... Kacchan was kind.
The body sinking to the depths of the sea would say otherwise, completely gutted and torn to strung-together parts, barely held together by delicate strings of muscle.
Kacchan smirked at him, his hand - which looked like it was dipped in grey ink all the way up to his elbow - cupping Izuku's, reminding the small man of their size difference. "You doubt me, De~ku?" The sound of Kacchan's baritone voice echoing from underneath the sea made Izuku tingle in spots he didn't want to think of, gulping down a sizeable wad of saliva. "N-No... I just wanna make sure Kacchan is okay," Izuku squeaked, leaning close as Kacchan flicked his powerful tail to push out from the depths he was stationary in, breaching the surface to grin at Izuku. Kacchan looked so handsome like this, hair dragged down by the ocean with cherry-stained ocean water trickling down his face and neck. "Shitty nerd, don't underestimate me; puny mongrel didn't stand a goddamn chance," Kacchan hummed, crowding Izuku onto his boat, pulling himself up with his sheer strength as he cornered Izuku against the driver's cabin, crowding Izuku against the cold wood. "Keh, fucker didn't even get a good hit before I cracked his body apart with my hands," Kacchan gloated, dripping cherry-stained seawater all over Izuku's deck, pulling his big body as close as possible.
"Mmm... you smell good," Kacchan mumbled, opening his mouth to show the sharp rows of teeth the blond had, rough tongue lolling out to lick up Izuku's cheek. "Taste good too, much better than that asshole." Kacchan huffs against his skin, blowing little microscopic water droplets against Izuku's skin as the blond nuzzled against his nose and cheek. "Ka-Kacchan," Izuku whispered, staring at the blond through lidded eyes, stroking up and down Kacchan's biceps, the smooth skin contracting under his touch. "Come into the water with me, 'Zuku," Kacchan whispers against his skin, anchoring himself seeing as not even half of Kacchan could fit on Izuku's little dingy seaboat. "Float with me; I'll keep you safe; nobody but me will touch you," Kacchan promises, that lush baritone voice making Izuku's mouth pop open to pant gently, eyes growing half-lidded and dewy with tears. "N-Not here, though," Izuku keens as Kacchan drags the tips of his sharp teeth along his collarbone; his faded sea shirt popped open from when he was sunbathing as Kacchan floated around lazily. "Hm?" Kacchan hummed questionably as he licked over the lines his teeth dragged into Izuku's skin, irritating the raised lines in a way that made Izuku shake.
His knees knocked against Kacchan's hips, pulling tight around the blond's body as his core simmered with lust, eyes dripping with dew and tears. "S-Somewhere else... not here, please?" Izuku whispered, staring up at Kacchan through clumped lashes. "I'll follow your boat. Don't take too long, though, or else I'll stall this little thing and fuck you against the hull after I drag you out of it," Kacchan chuckled as he pushed back, his weight pulling him off the ship and back into the crashing sea, seawater splashing over the lip of his boat. Izuku whimpered as his body pulsed, and his legs quivered as he managed to stand.
Izuku turns his little boat on after making sure Kacchan wasn't near the back of his boat; the shark mer already slicing through the water ahead, waiting for him. Izuku turned the motor on and pushed the lever forward slowly, inching his boat into a steady speed as he crested over the waves, bouncing with the tides that rolled in and out, leaving the cherry-stained sea behind. Izuku didn't spare a look back, didn't even look into the mirrors overhead to look. He just moved along quietly, stuck in his head.
-
"Deku," Katsuki crooned, staring at his little mate, who was dipping his little toes into the cool ocean water. "H-Huh?" Deku looked up, as cute as a goddamn sea bunny. "The sea ain't gonna eat you, baby," Katsuki chuffed, swimming close to poke at Deku's toe with his claw, making the little man giggle. "Now, get the fuck in here or else," Katsuki said bluntly, his cocks aching behind his slit, claspers fluttering with the need to lock around Deku's hips. Katsuki knew Deku was scared of the ocean because even though he had a fucking merman as a goddamn mate, the little fucker could not swim. Never learned how and Deku doesn't seem keen on learning anytime soon.
"Y-You'll catch me right, Kacchan?" Deku whispered, gently shucking the soft silk sea shirt off, bearing Izuku's pretty chest to the warm sun overhead, warming the waters just slightly, but the temperatures were still just above frigid as always. "No shit, nerd. I ain't gonna let my mate drown," Katsuki huffed, yawning as he floated closer, holding his arms out for Deku to jump into them once he rid himself of his shorts. As much as Katsuki would like to protect Deku's cute cunt and bubbly ass and keep it hidden in his shorts for only his viewing pleasure, the shorts would be coming off one way or another.
Torn off or taken off before he entered the water.
Deku clearly understood as he folded them along with his little panties, which were printed with little fish and sharks on them. Fucking nerd. "O-Okay, I'm coming in," Deku squeaked as he hopped off the boat, landing straight into Katsuki's arms, submerging Katsuki's face with the force of his little body landing in his arms and the splash Deku made as he entered. "Brr," Deku hummed as he settled on Katsuki's abdomen, making the blond hum as his abs flexed at the feeling of Deku's cunt settling on them, that little button-like clit nestled between a fat hood that peaked out of puffy folds. Katsuki had the pleasure of seeing them speared on his cocks and gaped, which was a goddamn sight to behold.
"Ah, Kacchan feels so soft," Deku mumbled, sliding up his chest to nuzzle against his cheek as Katsuki floated lazily on his back, claspers flapping around uselessly as he could feel the swell of his cocks starts to push at his slit. As much as he would love to bask in Deku's cuteness and squeeze that bubble butt in his hands all day, he wanted- no, needed to fuck Deku.
Now.
"Baby," Katsuki cooed as his hands trailed down Deku's spine, two fingers gliding through the crack of Deku's pert ass to circle around that cute little puckered hole before slipping deeper. Even though Katsuki wasn't fully submerged, the rippling water cresting and falling around his neck and jaw was enough to travel with the scent of Deku's arousal, smelling of sweet, lush victory and the salty seawater surrounding them. "A-Anh..." Deku keened, pushing his ass and hips back into Katsuki's hand, his fingers messing with the strands of slick flowing from Izuku's cunt. Katsuki growled at the sound, gills flaring as his slit split open to push his cocks out, spilling pre-cum into the water around them. The tapered tips slipped and were sandwiched between Deku's asscheeks, making Katsuki groan as Deku slid back just enough to rub against the cocks, humming as they bumped together at the lazy movements. Deku looked behind him, eyes going a pretty half-lidded as he reached back to slip his hands over the tapered tips. "Kacchan... if I bring the big boat around, do you think you would board it?" Deku asked, sliding his hand up and down the lengths of his cocks, pushing them apart as his middle finger rubbed between them. "F-Fuck, why?" Katsuki groaned, choking back sounds of agonized pleasure. Deku knew how to make him huff and writhe, and fuck Deku was trying to make him cum too early. "Wanna suck your cocks, but I can't out here," Deku pouted, sounding oh-so sad that he couldn't choke on his cocks like the whore he was.
"Fuck, if you bring the big boat around, I'll stuff you full and fuck your throat if you want," Katsuki groaned, pushing his head back as the crown of his head submerged under the water, listening to Izuku moan happily, spiked ears fluttering as his blood-red tooth earring jostles in his ear. "Grrngh...shit," Katsuki chokes out, gills flaring as his pleasure broils under his skin, akin to an underwater volcano boiling the water around it, ready to explode. Deku's little fingers dipped into the slits of his cocks one by one, teasing and smearing the diluted and dissolving pre-cum all over the heads of his cocks, huffing as his claspers tried to anchor around Deku's hips at the angle. They mostly just hugged Deku's thighs and inched around his hips, but it made Katsuki feel much better.
"Little shit, gonna make me cum," Katsuki groaned, glaring at Deku, who stared at him with half-lidded eyes, a giddy little smile gracing kissable lips. "Y'gonna let me fuck you, or are you just gonna - nngh - jack me off?" Katsuki choked out, fins stiffening and relaxing with each stroke from tip to base, each cock getting the same amount of agonizingly good attention. "D-Dunno, like seeing Kacchan's face like this," Deku giggled, moaning as Katsuki's abs flexed, rubbing against his clit. "Y-Y'r just asking to get fucked against the hull, huh?" Katsuki ground out, glaring at his mate who panted, face flushed as his hips worked in little lazy circles, smearing his cunt and clit all over Katsuki's abs and lower abdomen. Deku says nothing but drags his hips upward just enough to shift back and drop down, Katsuki's cocks pushing against Deku's cunt lips, crowding in between his legs. Deku hums and grinds his hips back and forth in little movements, water sloshing around his waist as he moans gently.
Katsuki watches enraptured as Deku's small, pudgy clit drags up and down his lengths, puffy hood looking too fucking cute against the long lengths of his cock. "S-Shit, baby," Katsuki groaned, fins rippling with each bolt of lust that crawls down his spine, his cheeks bleeding blush and making him feel flushed and light-headed. Not even the gentle waves crashing against his jaw and neck could calm him down as Katsuki guided Deku's rolling hips, pushing and pulling him to drag his cunt all over his cocks. "Just gunnin' to make me bust outside of ya', huh y' little shit?" Katsuki growls, leaning up to nip at Deku's chin, tasting the drool on soft pale skin dotted with freckles and a slow-growing tan. "N-Nuu... want Kacchan to fill me up," Deku keens mindlessly, eyes far away and hazed over as he grinds mindlessly, hips rolling with Katsuki's guiding movements. "Then get to it, Deku, or else there will be no fucking filling up," Katsuki hisses, thrashing his tail to jostle Deku slightly, grumbling as Deku leans forward, whimpering a little moan as he guides Katsuki's cock to rub against his cunt and hole, the other pulsing with need.
"Fucking cock-drunk bitch," Katsuki snarks, pumping his hips upward to shove at Deku's hole, tapered tip catching as Deku moans, his hand barely able to engulf the full girth of his cock to guide it deep inside his mate.
Deku is fucking tight. His cunt suffocates his cock as Katsuki pumps his hips in thrashing movements, churning the ocean as he fucks his cock as deep as he can go, splitting Deku open on his cock. Deku groans and throws his head back, bearing the collum of his throat to Katsuki, who licks off his spit-slick lips. His body aches with a pleasurable feeling, the places where the smaller shark mer's thrashing tail knocked and slammed against his buzzing with uncontained energy that makes Katsuki's skin swim in pleasure. The ache of his body and one cock shoved deep inside of Deku's tight cunt makes the blond groan, staring at Deku's slack face, his mate's breaths coming out in shaky little puffs that Katsuki longs to drink up, spit down Deku's throat and watch his bitch gurgle on it.
"Fuck, fuck," Katsuki chokes out, claspers suctioning and holding around Deku's hips as he fucks into his mate, pumping his hips in a steady, battering rhythm. Deku squeals and moans loudly, echoing through the dead and quiet sea all around them. Katsuki can feel the way his body screams at him and burns with the need to fuck Deku full, groaning as his teeth gnash together almost painfully. He knows he'll lose a few because shark skin is no soft thing, and tearing through it loosened a few of his teeth.
Maybe he'd give them to Deku to add to his weird hoard of Katsuki's teeth.
Deku leans down to moan loudly into his ear, losing his balance as he sinks even lower on Katsuki's cock, the second one pulsing wildly and bleeding pre-cum against Izuku's asscheek, chafing against Deku's soft asscheek. Katsuki hissed a gurgled sound of pleasure as his back starts to bow with each thrust, getting more and more desperate to pump his seed right into Deku's awaiting womb, claspers having gone rigid as Deku cinches tight around his cock. "Fuck, gonna pump you full, make you full of my pups..." Katsuki groans, hearing the moan Deku lets out vibrate against his drool-covered shoulder as Deku's fingers crawl around his waist. "You want that, bitch? Y'want me to fill your cunt full of my cum and breed you, hah?" Katsuki snarls as Deku's fingers crawl up Katsuki's sides, dipping into the rough ridges of his gills.
Katsuki chokes on a sound as his gills flare at the unfamiliar feeling of Deku's fingers crawling into the grooves, groaning right into Deku's ear as Deku's little fingers slide up and down the frills of his gills, making Katsuki thrash and buck hard into Deku. "Fuck, fuck! Grrragoddamnit," Katsuki groans out, mouth popped open as his hot breathes puff over Deku's ear, thrusts unsteady and hard as he fucks into Deku's cunt, reaching back to shakily guide his second one into Deku's gaped cunt. The tapered tip pushes in as Katsuki guides Deku down to the root of his cocks, watching Deku's cunt swallow them up and moan happily as they settle inside Deku perfectly. Deku's little fingers danced in the delicate frill membranes, sliding over the little ridges as Katsuki fucks into his mate desperately, trying not to show how much the gill-touching affects him.
He doesn't think it's working all that well as Deku's fingers slide up and down, moaning loudly as his cunt is obliterated and molded once again to his twin cocks, knees knocking against Katsuki's hips as Deku cums with a squeal. The water around Deku's cunt goes a soft milky white as Deku squirts, head thrown back impossibly far, the skin around the small bob of his Adam's apple pulled taut.
Deku looks perfect like this, cumming on his cock and screaming out his name like a madman who was possessed. "D-Don't stop! Oh god, don't-" Deku chokes another sound as his fingers in his gills dig into the sensitive membranes, making Katsuki's vision explode white as he cums hard. His body thrashes, and his teeth grit uncomfortably tight, hearing the loose ones creak as his mouth is filled with the iron taste of blood.
"FUCK!" Katsuki roars out, cherry-colored drool slipping down his jaw as Katsuki tries to stay afloat and still, not wanting to thrash too hard and flip them. Katsuki manages to crack his eyes open as his orgasm starts to subside, still clawing at the tips of his fins and down his tail. Deku is limp in his hold, gurgling little sounds of pleasure as his body twitches unwillingly. It's the perfect picture of the word erotic.
"SShit," Katsuki chokes, dislodging Deku's hands from his gills as water blows out of them; oxygen siphoned into his lungs as he tries to regain all the oxygen lost in his overwhelmingly powerful orgasm.
Note to self: don't let Deku near his gills.
Holy fuck.
Deku keens weakly as Katsuki holds Deku tight to his body, swishing his tail to haul them both to Deku's anchored boat, groaning as he uses all his power and might to gently drop Deku onto the deck on the towel laid out. Deku's legs spread uselessly as an arm covers hazy jade eyes, puffy and cum-filled cunt on full display for the lethargic mer.
Katsuki swishes his tail as he crawls up onto Deku's small deck, crunching himself into a curve shape - which is slightly hard because shark mers aren't very flexible in tight, cramped spots like Deku's tiny-ass ship deck - grunting as he rights himself. Katsuki lugs Deku's towel close to him, dragging his mate close, who looks up at the sudden movement. "H-Huh?! Anfh!" Deku moans loudly as Katsuki lolls his fat, rough tongue out to lap at Deku's cunt, eating up the slick and cum drooling out of him. "Taste good," Katsuki hums, massaging Deku's quivering thighs in his hands as he starts to lap and suckle at Deku's cunt. He's careful with his teeth because he knows they are far too sharp to be around Deku's cunt, but the thrill of the danger gets both of them going as Katsuki's cocks lay on his belly, still throbbing after cumming so hard. They drool little rivulets of cum and pre-cum down his smooth belly, marring his smooth hide in cum. "K-Kacchan," Deku cries out, bucking into his mouth gently, carding a hand through his hair and stroking the rigid and straight bones inside his fanned ears, groaning with little mewls. Katsuki hums as the sun warms his rough hide, soaking in the scent of Deku's cunt as he eats Deku out gently, knowing Deku was overly sensitive.
The afternoon followed a lazy time on Deku's private beach, with Katsuki sleeping in his den under Deku's dock as his mate slept inside. Eventually, Katsuki would find himself inside, slipping into Deku's weirdly soft human bed and cuddling close to the drooling nerd.
Maybe this time, Katsuki's sperm would finally take clutch.
Or next time, Katsuki would stall Deku's stupid dingy sailboat and fuck him against the hull as he promised.