Chapter Text
Katsuki’s only indication of time came from the passing of the sun overhead. At one point, he had learned to rely on the clocks on the walls outside of the warped, bubbled glass of his metaphorical testing tube. The clocks that Deku and his colleagues would wear on their watches irritated his sensitive ears. Deku stopped wearing watches over 365 days ago, which was approximately the number of times the sun passed overhead.
Katsuki no longer lived in a testing tube-shaped capsule, but he remembered it. It had been just large enough to fit three humans, suspended in water. It was just large enough to fit Katsuki and the extensive length of his scaled, finned tail. He used to keep his tail coiled at the bottom of the tube.
It had taken months for that poor posture to correct itself. His vertebrae had yet to fully readjust. Much of his tail had grown in that confinement, and for that reason, the end of his tail was perpetually crooked.
When Katsuki was first found, it was on the deck of a commercial salmon boat off of the coast of Alaska. The fishery had reported him and the flock of intrigued and territorial scientists that came by shortly thereafter nearly put the fishery underwater--in terms of finances, that is. The area Katsuki’s body was found was scoured from coastline to coastline and prompted an uproar among the fisheries in the area. When no other significant discoveries were found, they made away with Katsuki in a tank and that was the end of it.
Katsuki hadn’t seen the Gulf of Alaska since he was a teenager.
Approximately three years and an innumerable amount of needles and injections later, Katsuki met Deku. Or rather, Izuku Midoriya, as he was called by his colleagues.
Deku was on an internship at first. He had heard about Katsuki’s case through the grapevine of NDAs and confidential papers. A real life mermaid, merman, whatever it was the tabloids once tried to gain traction with. The stories were quick to fade out of the general public’s eye. No one really believed it.
Deku believed it, though.
Deku proceeded to do everything he could to simply get in contact with Katsuki. Katsuki vividly recalled the first day he saw Deku. They wouldn’t meet for another week and a half while Deku’s paperwork went through.
It was one of Katsuki’s least favorite days. He was groggy and nauseous and hadn’t been able to sleep since the clock’s small hand was over the two. It was the first two of the day, which meant it was morning. The most interaction he had was done over the periods he was unconscious, so he wasn’t entirely sure what that entailed. These days only happened once every couple weeks--when the clock’s small hand had gone over the “two” 24 times.
He was awake, though, to see the lab door open. Katsuki’s eyelids were heavy, stomach cramping, and muscles aching. It felt like someone had punched his arm repeatedly with a rock. It left him sluggish and borderline unresponsive when an unfamiliar face stepped into the room. He didn’t get too many of those.
This kid was bright-eyed and had all of the energy of an overexcited puppy--not that Katsuki had ever seen a puppy before. All curly black hair and an olive-toned face textured by a smattering of dark freckles. Katsuki assumed the glass hadn’t been cleaned, so they might not have been freckles at all.
The guy was talking to the project lead, animatedly, all hands and broad gestures. There was something… premeditated about the gestures, though. They were oddly specific, and Katsuki hadn’t noticed any of the other scientists use their hands that way before. Almost ritualistic.
Katsuki frowned.
And then, the guy noticed him.
That glow Katsuki had seen before dissolved in an instant. The guy’s smile wavered, left in an awkward in-between state of shock and horror. It wasn’t until the project lead took a few steps towards Katsuki that the stranger ever approached.
“It’s a bit groggy right now,” the lead said, staring up at Katsuki as Katsuki put a hand to the glass. The weight of his arm was heavier than usual. “This morning we had to take it out of the tank. Bi-monthly cleaning and blood samples.”
“And… no name still?” the guy said, eyes never leaving Katsuki’s. Katsuki was too distracted by the freckles. It was like someone had taken a paintbrush to the guy’s cheeks.
“No name,” the lead said. “We’ve shortened the subject name to Zero. Makes documentation easier.”
“I see.”
The last time Katsuki had seen a new human face, it was just before a biopsy. They had flown someone in to study him for a quarter and perform the surgery.
The human laid a hand flat over his chest before raising two fingers on either hand and tapping them together twice. He followed up with his pinkie raised in a quick, sweeping gesture. “My name is Izuku,” he said. He smiled when Katsuki slowly blinked at him, dumbfounded by how distracting this guy’s hand gestures were. Deku went on with more motions. “I’m here to teach you how to communicate, okay?”
_______
Working with Deku was… odd.
The first day Katsuki seriously spent with Deku, he was slightly less foggy-headed than usual. It had been several days since his injection, which was odd. They never missed a day.
“I know you can understand most Spanish and some English,” Deku said, still distracting Katsuki with his hands.
It was difficult not being distracted by them. They were peppered with bright white scars paler than the rest of Deku’s otherwise tanned skin. The scars were even more distracting than Deku’s ridiculous freckles.
But Katsuki gathered what the bastard was telling him. He narrowed his eyes. There was a reason he kept his intelligence to himself. He was getting better with English and how to use numbers, specifically, as well as the obnoxious mouthful of terminology the project lead used with her underlings. This didn’t change the fact that he could physically speak the language back.
He knew he couldn’t, because they had tried. And now his vocal chords were fucked up to some degree.
“There’s a version of spoken language that has the same linguistic properties, but you don’t have to speak it to use it,” Deku said. “Have you heard of sign language?”
Katsuki simply stared back. He had never heard of it before. Like hell he’d comply with this cocky bastard, though.
Deku was patient, though. When Katsuki remained unresponsive that day, he simply came back the next day. And the next. And the next. Despite Katsuki’s physical and verbal silence, Deku began conducting lessons in earnest. He learned about grammar and sentence structure. He even learned that there were other languages, ones that he might never understand, and ones closest to what he was familiar with.
There’s a difference between Deku and the other idiots on the project. Katsuki was hesitant to lean into it, though. While the exams were less draining, Katsuki was still kept on a lower conscious frequency. The general grogginess he felt was still there as he wrapped his head around Deku’s physical language, all while remaining aloof and unresponsive.
It made the project lead frustrated, but that was usual when it came to Katsuki’s general disdain for giving her a reaction. Every now and then Katsuki began witnessing her increased frustration with Deku as months went by without progress.
“I know he’s--”
“If he can’t produce a single word by the end of this week, I can’t afford to have you in our study.”
Katsuki watched the lead walk off, her heels clicking on the tiles. She cast one last annoyed glance in Katsuki’s direction before shutting the door behind her. Deku had yet to turn back around, but Katsuki’s keen hearing could gather that Deku was crying.
Deku brushed his tears aside, though, and reassembled his resolve. When he turned back around, the only indication of breaking came in the form of pink eyes and cheeks. “Okay, I know what to do,” he said.
And then, Deku approached the tube where Katsuki hovered in the large coil of his tail. Deku put a hand on the glass, his eyes wary and concerned. “You aren’t going to like this, but it’s for the best,” Deku promised. He followed up with a smile as a sense of unease pooled in Katsuki’s gut. “I promise things will be better after this week. Just trust me.”
It took just one day for Katsuki to realize what Deku’s plan was.
He hadn’t eaten in over twenty-four hours.
Every now and then, this was typical before an exam. But he wasn’t due for an exam, as far as he was concerned. Deku was adamant on teaching him sign language for terminology around the tests that were due to be performed, which often came in the form of the actual, literal schedule. Deku would have told him if one such exam was taking place, if only to teach him the word for it.
Katsuki simmered in a boiling pot of fury. As if being antagonized wasn’t bad enough--Deku seemed to assume Katsuki was easily irritated by having his intelligence degraded (which he was)--he couldn’t believe Deku would take it this far. To put his health on the line, and that the people involved consented to it.
Deku came back on the second day and, without any spoken words, asked, “Tell me what you want.”
It took a severe amount of self control to stop himself from flipping Deku off.
“I can’t give you what you want if you don’t tell me what it is,” Deku signed.
Fuck you, Katsuki thought, feeling simultaneously nauseous and empty, as if there was anything in his stomach to feel nauseous about. The thought of even getting what he wanted felt unappetizing—until the third day. Katsuki’s tail had lost its color and turned a sick sort of iridescent grey. It lost its shine on the fourth day when he finally broke.
Deku was barely through the door when he froze at the sight of Katsuki, sunken to the floor of the tank, the tips of the fingers of one hand pressed to his lips. Katsuki’s nails had been cauterized years ago after he had severely injured several attendants and gave a near-fatal, poisoned cut to another. The hardened, scarred pads of his fingers tapped at his pale lips again.
Deku overcame his shock to wave one of Katsuki’s handlers over to get him food.
Katsuki was ravenous. Before captivity, Katsuki would shed his teeth annually after his new ones grew in, sharper than before. After captivity, his already pale scales turned even fainter, and his teeth dulled until the exact moment he was given food when asked.
The duller caps on his teeth shed off within a single bite. They cracked and splintered away from his gums, and by the second helping, Katsuki was sporting a fresh set of sharpened teeth. He devoured the oversized bait in less than three bites.
All the while, Deku stared at him in awe. Katsuki found the guy’s fascination less… greedy than the other scientists. Deku marveled. The others grew irritant with Katsuki’s attitude over the years. They were extortionists.
Deku was enraptured. Katsuki had his figurative claws hooked on Deku’s nerdy little heart.
This could be useful, Katsuki thought, especially as it occurred to him that the rest of the team had yet to understand the advantage Deku had given him: language, a form of it that the rest of the team didn’t know. Deku was his translator.
Katsuki didn’t exactly have a reason not to talk now, and not talking just encouraged his handlers to keep Katsuki’s food all to themselves, taunting him. It happened the very next day before Deku’s shift was due, and one of the handlers asked Katsuki to say something, which he didn’t, which prompted his food to be teased just out of reach after the lid was lifted.
The top of the tank was encircled at a distance by a metal walking path. At one point, when Katsuki used to have claws, he had been able to hook the railing. Now, he couldn’t reach it.
One of the attendants let out a startled laugh when Katsuki bared his teeth. “The new teeth are mildly terrifying, wouldn’t you say?”
“I heard that speech pathologist kid called dibs on the old teeth,” the other guy said, waving the mackerel about by the smooth underbelly. It was still alive, beady eyes wide and mouth agape.
The mackerel gave an aggressive toss, prompting the worker to drop it off the side of the railing. Katsuki nearly lunged or it, but it was too late. Katsuki shot a glare up at the guy, fingers curled tight over the lip of the tank.
“That was the last one,” the attendant said, slapping his coworker in the arm.
Katsuki flipped them off. An amazed, startled gasp spread between them. “Did you see that? Amazing! That kid really is onto something.”
The door to the lab slammed shut. Katsuki startled, glancing back to see none other than Deku crossing the tile. Deku’s expression was flat as he approached the tank and the now-dead fish on the ground. He reached down to grab it and toss it up to Katsuki’s waiting hands.
“You two can leave,” Deku said as he checked his watch. “I have the room until three.”
“Right! Have fun, doc!” one of them said as the other waved. The two of them descended the track while Deku climbed it, arriving at eye level with Katsuki around the same time the two workers vanished from the room. The door rattled behind them.
Deku sighed as he sat cross-legged on the metal grate. He flattened his notebook out on his lap and signed, “I’m sorry you have to deal with them.”
Katsuki merely glared. He flicked the spine of the mackerel over the glass ridge before ducking underwater up to his nose. His eyes blinked slowly, his haw retracting slowly as his eyes began to dry out. From what Deku has mentioned about the membrane, it was white and made it appear as though his irises and pupils vanished when it didn’t retract immediately upon blinking.
This was the bastard who got the bright idea to starve Katsuki. He knew he shouldn’t have trusted Deku.
Deku’s brow pinched with guilt. “I’m sorry, really. I know you don’t want to talk, but it’s the only way I can see you.”
Like I care, Katsuki thought.
“Can I continue teaching you?” he signed, eyes bright and cautiously hopeful.
Katsuki closed his eyes and sunk under. His hair lifted and slowly dipped beneath the surface after him. Deku leant against the railing to peer down at him, and when it became clear that Katsuki wasn’t coming back up for air, Deku chased him down the stairs, notebook in hand. The second Deku’s feet hit the ground floor, Katsuki returned to the surface.
Deku sighed and ultimately decided not to play this game. Katsuki folded his arms over the ledge, still scowling, and made sure he faced away from Deku as Deku shouted, “I tried playing nice!”
Deku marched around the tube to where Katsuki had his eyes focused on the wall ahead, pointedly ignoring Deku’s puppy-dog stare from the ground. Deku just went on, not speaking a word as he signed just how sorry he was. Katsuki scowled, jaw ticking. He wanted to see what Deku was saying, but that meant looking at the bastard.
Eventually, Deku had gone on for so long following Katsuki around the tank in hopes of getting him to watch his apology, that Katsuki relented at the simple spelling of a word: escape.
I definitely didn’t see that right, Katsuki thought, but he was intrigued enough to glance at Deku.
“I can’t help you escape if we aren’t on the same page,” Deku signed. At least, Katsuki thought that was what he saw. But as he signed it, Deku verbally said, “I can’t help you if we aren’t on the same page.”
He’s fucking with me, isn’t he? Katsuki thought.
“Let’s start with something simple,” Deku said. “Can you tell me your name?”
Katsuki had a name, but it wasn’t something he could sign with the tools Deku had given him. He shook his head as he tapped his index finger and middle finger to his thumb before twisting his wrists, index fingers loosely extended. No translate.
“It doesn’t translate?” Deku repeated with proper LSP grammar.
Katsuki nodded his fist. Yes.
Deku beamed at him, stepping closer. “Okay, that’s good. I mean, that isn’t good because I can’t use your name. Can you show me it anyway?”
It was at a frequency Katsuki wasn’t entirely sure Deku could hear, and when Deku didn’t respond to it, Katsuki signed, “I just said it.”
“I thought I heard something,” Deku confessed with an apologetic smile. “I guess my ears aren’t good enough. Do you mind if I record you?”
They spent the rest of the time working with Katsuki’s handlers—or rather, Deku spent the rest of the time that way. Getting clearance to drop Deku’s equipment into the tank was more complicated than Katsuki thought, and it took another week before Deku was able to record anything.
Katsuki was muzzled for the occasion, and his hands would have been bound if it weren’t for the fact that Deku still needed him to sign. The microphone was caged and lowered into the water. Katsuki didn’t particularly enjoy the buzz it gave off, or the fact that he needed to wear a cage over his teeth. The microphone would have been shredded by now if his teeth were given access to it, though.
He signed, “I don’t like the noise.”
“I know you don’t. Just humor me for five minutes,” Deku said.
Katsuki glared at him. Deku looked up from his computer a moment later to meet Katsuki’s furious glare.
“Could you tell me your name again?”
Katsuki did, and Deku’s assistant pointed to the screen. Deku tapped a button and the buzzing went away. They fiddled with the audio clip before recording another.
Katsuki leaned closer to hear when Deku and his assistant put on their headphones. The audio was muffled, but when Deku caught sight of Katsuki’s eyes on them, he turned the computer screen around to show Katsuki the digital wavelengths. When Deku tried to play the audio on the speakers for him, Katsuki thought his eardrums might rupture.
That can’t be my voice, Katsuki thought, irritated as he rubbed at his sharp, flattened ears.
“I think we could work with this,” Deku’s assistant said. “This is proof that there are others, and that they socialize. Why else would he have a name?”
“He understands Spanish,” Deku reminded her. “He could have had contact with humans before.”
“Yeah, because a human would give him this name,” she said, gesturing to the headphones where the audio clip was still playing on repeat. It was muted, though, and less irritating to Katsuki’s ears.
Katsuki glared at her as she made off with a sample of the clip and promised to show it to the project lead.
“Could you say my name?” Deku asked, and when Katsuki didn’t answer, Deku flicked on the microphone again.
Katsuki winced. He put up his middle finger, and Deku laughed.
The months went on. Deku spent the majority of his time charting Katsuki’s language and speech patterns. For the study director, this was all in hopes of understanding where, specifically, Katsuki originated. They had the general location (Peruvian sea caves), and there was a chance that they could trace the vocal patterns of Katsuki’s people like a radar. It would be easier to find more of his kind the more they expanded on his library of vocals.
The sea caves off of the coast of Peru were discovered in the early 2000s, and the intricate web was estimated to measure over 400 kilometers. It was the largest known network of sea caves, rivaling the Yucatán Peninsula’s Sac Actun and Dos Ojos cave systems. As far as the scientific community was concerned, the Peruvian caves were where Katsuki grew up. How he wound up in Alaska was another story entirely. It was all theory.
Until similar recordings were discovered approximately fifty miles off of the coast.
It was during this discovery that Katsuki woke up in the dead of the lab’s off-hours to the sound of a door opening.
His eyes focused, the glow reflected off of the glass as two silhouettes stretched into the room. Neither of them turned on the lights. A cart was being wheeled into the room, its creaking grating on Katsuki’s eardrums. Someone hissed to be quieter.
One such individual approached the glass, eyes turning up to meet Katsuki’s. Deku, and he came with that damn assistant of his.
Deku signed to him, “We’re gonna get you out of here.”
“OK,” Katsuki signed back.