Chapter Text
Izuku was born in captivity.
His mother had been a captive tropical mermaid, his father, a feral cold-water merman. He’d been born to them leaning heavily in color and shape towards the tropic, but with the size, strength, and longing for the ocean as cold-water. His growth through the years was carefully watched by his mother, his father long sold, and eventually, when she died of loss and heartbreaking grief, Izuku was left alone but well-cared for in a larger enclosure via Yagi-san’s sponsorship and conservation efforts.
One wall looked out into the ocean itself, a great glass window between him and whatever freedom lay beyond. There was never anything other than fish on that side, perhaps the occasional enterprising seal or otter. It was, however, a better view than the other other side, where small humans and large humans pressed their oily faces to his glass to stare at him, open mouthed.
Sometimes the children were cute, sometimes their eyes sparkled as he played and spun in circles, but there were so many of them, it grew old.
There was the noise from above, of someone tapping a metal bucket.
“Young one,” boomed a warm voice, his carer, Yagi-san, filtered through the water, “come on, Young Izuku, I have a birthday treat for you here.”
Tempted to remain at the window, lounging in his sand and brushing his limbs with the water fern, Izuku sighs bubbles and ascends, his powerful tail sluggish and slow. The enclosure just wasn’t large enough for him to go his top speed, he’d bang into the sides and edges, leaving him with the scattered scars and deep pressure cuts that healed so slowly in this filtered water.
He wondered what ocean water tasted like, if it was clearer, or perhaps, muddier? It would be so interesting to taste it. To stretch.
Izuku’s green mop of hair breaks the surface, the water laying it flat over his face. He pushes it away, grumbling, blinking in the sunlight to find Yagi-san squatting down next to his water, a welcoming smile on his face.
As humans go, Yagi-san is definitely Izuku’s favorite.
Chirping at him, Izuku swims closer, laying his arms up over the ledge beside the man. There were few people in the world that Izuku knew wouldn’t hurt him, and Yagi-san had proved to be the number one.
“Hello, young one.” Yagi greets, sitting carefully and letting his legs dangle in Izuku’s water. It was a dangerous move, most trainers considered it to be, but Yagi had been with Izuku his whole life.
“Hello, Yagi-san.” Izuku mouths carefully, voice box inhuman and clicking but managing the words with some degree of accuracy. Human words required air in the lungs instead of water, so it took a period of adjustment each time. He beams at his success, and Yagi pets his hair like he normally does, proud.
“It’s your birthday, Izuku.” Yagi tells him, and Izuku perks up, expecting his usual birthday gift of mollusks, scallops, and oysters of various kinds. Yagi does give him his bucket of seafood, which makes Izuku preen and chirp in excitement, but speaks before Izuku can fall back and swim away with it.
“Tomorrow, we’re introducing you to Yuurei’s newest resident. A merman, much like you, who was rescued off the coast of Barbados.” Yagi tells him, and while Izuku does speak the human language – it’s impossible not to pick it up – he can’t quite believe what he was saying.
He trills questions in his language – who is he? What is he like? What does he look like? Rescued, does that mean saved or taken? – but Yagi only holds his hands up to slow the tide of incomprehensible ocean-speak.
“I don’t know much, but I know the higher ups want you two to meet.” Something sad enters his expression. Or was it hesitation? Izuku had a hard time with human emotions, they had no frills or fronds to display them. “Hopefully you like him, and he likes you. You’re special, Izuku, you know that? You’d make beautiful children.”
Children? He means babies? Pups? Izuku will be making pups with this new merman?
He tilts his head and paws with his non-bucket hand onto Yagi’s wetsuit, questioning. Yagi sighs, muffling a cough with a sickly hand. Frowning, Izuku warbles a few notes of song his mother taught him, and Yagi smiles in appreciation.
“All Might, sir~!” Midnight, another trainer, one who worked with the killer orcas several enclosures over, calls out from the office walls.
“Thank you, my boy.” Yagi pets him again, before removing his legs from Izuku’s waters. He hasn’t answered any of Izuku’s questions, but that’s not new.
A new merman. Izuku snacks on his treats, then has fun dragging the bucket around in the water in front of what looks like a small pod of human children, chaperoned by a woman who vaguely reminded him of his mother, but turned human with legs. He wonders what this new merman will be like.
“This him?” Kirishima grins, waving his hand a bit when the green haired merman carefully sticks his head out from his greenery. He’s cute.
“Yes, this is young Izuku. His mother Inko passed nearly five years ago, so he’s been alone for a long time.” Yagi-sensei answers, rubbing a hand through his hair. “His enrichment has suffered.” They’re in the public’s underground viewing area, thankfully the aquarium was closed on Mondays.
Izuku tilts his head and chirps at them, though they hear nothing through the water and the thick glass. Working his way from the foliage, Kirishima is surprised by the merman’s obvious health and fitness, with strong shoulders, a powerfully thick tail, and scars slicing up his midriff and arms.
And his colors. Iridescent green scales that flicker blue depending on the light reflection, his frills are all white, black, or green and stand from his hair directly instead of the typical two fins behind the ears Kirishima is familiar with. He looked like a curly dandelion puff actually, with his multi-coloured fronds and frills on his forearms and shoulders. His gills were so thin too, lined up on his ribs, sleeker than Kirishima has ever seen. Even with the sharp teeth and sharp claws that are typical of a mer, Izuku was nearly harmless looking, alien to human eyes and a creature of the water. Beautiful, absolutely beautiful. Despite working with mers for more of his adult career, Kirishima still found his breath stolen now and again.
“He’s cross-bred, his mother was tropical, which means he’s the only male able to bear in captivity.” Yagi-sensei tells him, seeing how Kirishima was so distracted by the way the merman looked. Interested in the new human, Izuku drifted closer to swim sideways beside them, taking in the new person and Yagi. Izuku waves directly at Yagi happily, swirling in pleasure, and it makes them both laugh.
“He’s bigger than I thought, that’s good. Mean’s he can protect himself.” Kirishima grins while Yagi-sensei groans, rubbing his face.
“If this one is as violent as everyone says, why are we putting him in with Izuku? The boy has a hard time killing his own fish to eat them.” Yagi-sensei smiles in greeting at Izuku, who swims close enough to put his hands on the glass. He’s fearless this one, Kirishima thinks in excitement. Kirishima grins at him, and Izuku blinks at the sharp teeth in what seems like a normal human. He checks on the legs, nope, still two human legs, and then back up to the mouthful of teeth. His interest and thought process was captivating.
Izuku grins back with his sharp teeth, baring them in challenge, and Kirishima laughs.
“He’ll be fine!”
Izuku is not fine.
He’s been put in the split corridor that connects so many of their enclosures, and urged with inflated walls down somewhere to perhaps, meet this merman? But he was nervous. He’s trilling and keening and warbling to get someone to talk to him, even a human at this point, but nothing.
The red-haired man he was so sure was a walking merman was up ahead, knelt by the new arrivals bin, which was essentially a cozy small tank with a few plants and clear walls. As Izuku approaches, tentative, he can see a large shadow moving inside. Big. Very big.
Izuku almost doesn’t want to look, but his curiosity in meeting another merman overran his fears.
He came up to the clear divider but couldn’t see anyone. The tank was basically empty, but perhaps he was hiding in the plants? Izuku tries out a small trill, a careful greeting. Nothing. He turns his head and blinks up at the red-haired man who squatted above in the open air. There was something tight in his expression, so Izuku glances back, and immediately recoils.
A pale haired merman with burning red eyes was mere feet and a bit of plastic away, with a great big black tail, scales lifting in aggression and shining red underneath. Large powerful arms on either side of the doorway, muscles bulging, frills which were spikier than Izuku had ever seen on any mermaid before, and a snarl so vicious Izuku felt the teeth in his skin already.
“The fuck are you?!” The other merman roars, throat clicking with rage. Drawing further away out of range, Izuku sways in agitation. He’s obviously dangerous, could kill Izuku in an instant if he wasn’t careful. But he was also gorgeous. Powerful. His voice was deep and rough and his hands looked large and strong.
“Answer me!” the black tailed one snarls again, landing a fist against the plastic. It shakes, but doesn’t break, and it makes the red-haired human above click his tongue and chide him.
“Katsuki, bro, really, don’t scare him. Isn’t he pretty? Isn’t he nice looking?” He coos, and the apparent Katsuki snarls up at him instead, splashing at him. “Dude.” Kirishima complains. It’s clear the red-haired man has been around this large black tailed merman for a while, he didn’t take it personally, but he was still careful to remain out of reach.
“Izuku.” Izuku tries to say, confidently, but ending on a squeak. His tail whirs underneath him, curling up to hide some of his body and internal organs from the drilling gaze of those red eyes.
“What?!” Katsuki growls, “Deku?” He laughs, almost cruelly, but mostly with pent up aggression. “Is that your fucking name, your name is useless? Fucking deku—”
“I-Izuku!” He shouts, pushing closer just to float up and meet the frightening mer. He puffs his fronds up in challenge, and partly, in performance. “My mother named me Izuku.” Katsuki’s shoulders bulge at the display, teeth large and gritted at Izuku, and he shows his teeth right back. It was good with the plastic in between, Izuku wasn’t sure he would win a dominance fight with this one. And even then, if the pale blonde won his dominance, would he stop before he killed him? Izuku didn’t want to die.
Honestly, Izuku wouldn’t mind terribly to submit to this utterly beautiful and strong and capable merman, but only if it were for a good reason.
Above them, they hear the humans speaking. Yagi-san sounds a little alarmed, but Kirishima is trying to talk him down.
It seems though that his defense has proven something to the wild merman, who lets his scales relax just a bit. Izuku almost mourns the loss of the red, but there’s enough agitation in the other that the scales on his tail shift constantly. It’s beautiful, and distracting.
He has a few scars, just like Izuku, but they’re all lined up perfectly like claw slices, or are rough and torn like bites. He’s seen battle. None seemed fresh, however, what could have caused the humans to rescue him?
“I’m gonna call you Deku anyways.” Katsuki grouses, eyes flickering up at the humans and then over Izuku. “They do that to you?” He juts his chin out at Izuku’s scars.
“Oh.” Izuku also looks down at them, trailing a finger over the worst on his arms and stomach. He glances up and finds the red eyes taking him in, from the tops of his hair fronds to the tips of his tail fins. Preening a bit, shifting so his colors shine, Izuku answers him blithely. “No, I did these to myself mostly. Yagi-san says I’m bored and not entertained enough. I think I just want to go fast.”
Katsuki snorts, then with one more dominance performance, ear fins fluttering and tail scales revolving from their black to show their danger red, he seems to relax and floats away. Without the look of rage and hate on his face, which Izuku could tell through the scents and twitches of his fronds wasn’t really that intense, he was quite lovely looking.
Kirishima says something with relief and pride, and Katsuki grimaces up at him.
“I like your human carer.” Izuku tells him, pressing both hands to the plastic between them. Perhaps Katsuki doesn’t want to kill him after all? Does Izuku have a new friend? A friend that would…gulp…give him babies? The words were a mistake, however.
“He’s not my human! Or my carer!” Katsuki screams at him, whirling and puffing out like a blowfish. Izuku, unimpressed, merely blinks at him, preening his fingers through his hair a bit. He catches Katsuki eyeing the way they sift through dark green strands, shining with the mix of white fronds within it and smiles, biting his lip. Caught, Katsuki growls dangerously once, then turns and dives into the greenery.
“I’ll see you later! Maybe they’ll let me inside!” Izuku calls after him, pleased. Kirishima is slowly spreading the inflatable wall between them though, so Izuku sighs and wishes for one last look at the beautiful black and red scales.
He pops his head out from the water to greet Yagi-san and Katsuki’s human.
“So, how was that, young one?”
“O-kay.” Izuku clicks the human word back at him, and Kirishima nearly trips, arms flailing. Alarmed, both Izuku and Yagi watch him catch his balance. Despite the red-haired man’s obvious affection for Katsuki, Izuku was pretty sure the blonde would kill the man if he fell into his enclosure.
“He speaks?!” Kirishima demands, looking from blonde man to green haired merman in wonder and astonishment.
“Only a bit, it’s hard on his vocal cords, they don’t have the same as we do.” Yagi smiles though, proud, and reaches forward to pat Izuku’s head. The amount of heart attacks Yagi has given Aizawa, head of security and workplace safety, is off the charts simply because he does things like this. Kirishima gapes. Izuku, however, simply lets him touch, smiling with all his teeth.
“I’m glad you were able to connect with him, young Izuku.” Yagi-san praises him. “It couldn’t have been easy.” Izuku trills and puts his arm up in the air to show his bicep and gives them a deep look of determination and both of them laugh.
“He lets you pet him.” Kirishima whispers to himself, staring, “and he knows manly jokes. This is great.”
“I’ve been with Izuku his whole life.” Yagi explains, and they start moving with Izuku back to his enclosure.
Stopping, Izuku turns back to the blocked off wall that hid his new friend from view.
“Bye Kacch-an!” He chirps into the air, in human speak, and grins to himself when immediately, from over the wall, he can hear a scream. Both humans blink at the unintelligible mer-speak from Katsuki’s arrival room, and at Izuku’s smug expression.
“The fuck did you just call me?! I’ll fucking kill you!”
Izuku giggles, and then rushes impatiently back to his enclosure so he can spring clean. Later that day, the humans found a small pile of faded, water-logged cloth, stale, old strings of seaweed, chipped clam shells, and a long wire long rusted on the water’s edge.