Archive of Our Own

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A mermaid's worst nightmare had happened to Sukuna: he was trapped in a rocky pool after a turbulent storm dragged him ashore, leaving him where any human could see and capture him. At most, there were some slippery sea snails hiding in small crevices, shallow moss clinging to rocky outcrops, and half-dead corals lining the sandy bottom below. Furthermore, it took him about four seconds to swim in circles and back to his starting point.

He poked his head above the surface during the darkness of the night and revealed the waves rolling in the distance, too much to drag his body without scraping off all his scales or drying him completely. So, for the time being, he remained completely trapped in that small body of water.

He'd never encountered many humans traveling along that beach, so the best he could hope for was another storm to raise the tide. That way, at least he wouldn't have to worry about drying his scales while crawling toward the ocean. He could regenerate them, fuck it. But he couldn't stay there forever! 

Sukuna's only means of sustenance was the minimal amount of plant and animal life around him; unfortunately, it slowly dwindled while he remained trapped there. He could already see his own ribs...

And then the worst thing that could happen, happened: a human discovered him.

Sukuna dove into the pool as he felt the tremors of approaching footsteps, partially hidden beneath a rocky outcrop. However, he could already hear the human speaking loudly and splashing water a few times.

Until a stone was thrown at him.

It narrowly missed with its tail, but the gesture alone was enough to send Sukuna swimming out of its hiding place at the bottom. It spotted the human's silhouette and immediately launched itself towards him with a powerful tail flick, its lips twisted into a growl as it leaped out of the water, not going very far, just enough to reach the human.

The human screamed as he narrowly dodged the merman's attack, fell, and struggled frantically with those pathetic legs he possessed.

Satisfied that the threat had vanished, Sukuna slowly dragged himself back into the water, wincing at the sight of the sharp stones embedded in the glistening scales. At least the water soothed the discomfort, but nothing but fresh food would ease his rumbling stomach. 

Damn, maybe I should have eaten that human instead of scaring him?

No, that would only result in more humans coming in search of their lost friend. Terrible idea. Barely a minute passed in the water before the shadow returned. Its crimson eyes fixed on the human above, lips pulled back in a mocking smile, and it quickly moved away. Sukuna slowly relaxed again, only for the same head to reappear seconds later. 

Did he/she have a death wish?

 He was smart enough not to throw stones this time; he watched silently as Sukuna turned and hid in the shadows to avoid the hot midday sun. At least in the ocean he could hide from the heat, but here he was boiling alive like in hydrothermal vents! The human disappeared soon after. Sukuna watched the edge of the rocky pool, but he didn't reappear so quickly. When the merman slowly reached the surface and put the top of his coral hair and horns out, he saw the human walking away, leaping over the rocks, with a giant piece of wood in his hand.

Well, at least that one seemed harmless and didn't plan on trying to kill Sukuna while he was trapped. But the clouds were few, very light, and there was no sign of rain. Would he really die there? Trapped in a small puddle of water? Of hunger? He couldn't risk trying to crawl to the ocean in the middle of the day, and with each passing day he grew weaker without sustenance.

Perhaps he would try that night...

But after another hour of tedious emptiness, the trembling of approaching footsteps caught Sukuna's attention. He looked up as a silhouette appeared.

Something was thrown into the water. 

Sukuna growled, ready to attack the annoying human, when he realized it wasn't a rock. It was a fish. Already dead, but a fish nonetheless! Hunger took over, and he lunged toward the meal and devoured it without hesitation. 

Finally!

It had been so long since he'd eaten proper food! Sukuna couldn't hide the small gurgles of satisfaction that escaped his chest as he ate, careful not to waste a single morsel. Once everything was eaten and Sukuna picked bones from between his teeth, he looked back at the human who was now crouching at the edge of the pool, silently watching him. Perhaps that human could help him, or at least bring more food so he wouldn't die. Very slowly, Sukuna floated towards the surface, careful not to startle the person. 

The human still leaned back, startled by the approach, however slow it might be. He fell in surprise when Sukuna's dark red horns broke through the surface, followed by the rest of its head. Beside him was a large, round, shiny white object, but Sukuna couldn't see what was inside. And that staff he had before was out of reach.

But the human didn't look away; their gazes locked as Sukuna gave a small twitch of his tail and approached timidly, cautiously and suspiciously. When he reached the edge of the rocky pool and sat there, his second eyelid blinking to keep his eyes moist, the human finally moved again. Sukuna watched intently as he reached into the white thing and pulled out another dead fish. 

The fins on either side of his face widened. Instead of throwing him away, the pink-haired boy grabbed him by the tail and offered him up.

Sukuna waited another second, looking at the human, but... it seemed quite harmless. So, with equally cautious movements, the merman extended its hand and accepted the offered food.

The human smiled and laughed.

Sukuna stayed nearby while he ate, keeping a watchful eye on the boy as he peeled the fish, savoring the eyes to the very end and spitting out the hard pieces of cartilage.

"Do you speak my language?"

 He heard a voice and then he paused; he looked at the human who was speaking in his nonsensical language. 

What were you saying?

Sukuna snorted as he licked the remaining scales from his hands and washed away any residue. His stomach was more than satisfied with the fresh meal, so when the human offered another fish, Sukuna took it as before and saved it for later. When he didn't eat, the boy tilted his head and talked a little more. 

"Are you full yet? You're too thin, you need to eat." 

Sukuna blinked slowly. He didn't understand anything the creature was saying. Fortunately, the human had also come to the same conclusion. He began gesturing with his hands. With his palm against his chest, he repeated the same word over and over, pronouncing it slowly. Sukuna's brow tightened as he stood up higher, holding onto the edge, leaning closer to hear better.

"Yuji, Yyyuuuuuuujii," the human said, dragging out the word. "My name is Yuuuujiiii."

What kind of vocabulary was that? Was it supposed to be imitation? The sounds came out distorted thanks to Sukuna's sharp teeth and forked tongue, but he still managed to pronounce it: 

"Yujjjj."

Bright golden eyes lit up, hands clapped in a loud, surprising noise that made Sukuna squirm and hiss softly. The human rambled on again. Yuji, huh? Was that his name? Well, at least that human seemed nice; it didn't make you want to cut his head off. Sukuna held the fish in his hands, shaking it with a low clicking sound.

The human frowned and raised both hands, shrugging his shoulders. Confused. He didn't understand. Damn... Something made a strange buzzing sound, and Yuji reached into the strange human clothes, pulled out a small, black thing, and looked at it. He said something else and quickly stood up. Sukuna watched silently. He said something else that the merman didn't understand.

Then the boy tipped over the white container; a wave of water and three more fish fell into the rocky pool beside Sukuna. The merman's eyes widened as he swam to retrieve them all, even though they were dead.

That human really saved your life, huh?

"I need to talk to the teacher."

As Yuji walked away, staff and white object in hand, Sukuna let out a loud growl, drawing his attention. The human waved and continued walking away, disappearing into the distance. Perhaps he would never see that human again...

That was a lie, of course.

Sukuna didn't risk dragging himself along the rocky beach; he slowly nibbled at the fish he'd been given to last as long as possible. Another storm was all he needed. The high tides and rain would carry him away.

The next day, Sukuna saw a recognizable shadow appear high above. Had he returned? 

The merman floated to the surface, winked, and gurgled a "Yujj" in greeting.

"Hi, I'm back!"

The boy smiled back, his lips parted wide to reveal pale, white teeth. Weak little humans. He pulled that small black rectangular thing, hid his face behind it for a second, and then said something again. Sukuna frowned. The human patted his chest, repeating the same movement from yesterday.

With his flippers flapping, Sukuna murmured, "Yuujjjji?"

The boy nodded in response, smiled broadly, and quickly put away the small device. He leaned forward, surprisingly bold as he entered Sukuna's space and peered into the water, pointing and asking something else.

Yes, no, Sukuna couldn't understand anything that the boy with the funny hair was saying.

This didn't seem to matter, because Yuji continued rambling in his strange dialect and raised the stick again. Sukuna narrowed his eyes when he got too close to him. Fortunately, Yuji stood up soon after and pointed towards the ocean, with the white container in his hand. All Sukuna could do was watch with curiosity as the human headed towards the ocean with his peculiar equipment.

"Let's get you some more food."

From a distance, he watched as Yuji fiddled with the long pole, waving it back and forth in the water, and then stood there, completely still.

Sukuna quickly grew bored, but he didn't really have anything else to do besides watch the human. After a few minutes, almost as if by magic, he saw Yuji begin to move strangely and, within seconds, pull a fish from the ocean.

Humans and their strange devices... I'd never understand.

When Yuji returned with a bucket full of fish, Sukuna squinted at the strange rod that had caught them, noticing a weak, almost invisible thread on it. That must have been what dragged them to dry land. Well, at least he wouldn't have to worry about starving anymore. However, he remained trapped there until the rains arrived. Yuji kept him company, in his strange human ways. He always visited and chatted, and soon took Sukuna's name from him.

His pronunciation was so messed up, but at least Sukuna could still understand what the boy was saying. And he learned a few other things from the human too. "Fish," "fishing rod," "bucket," "telephone."

 The phone still confused him, but Yuji wouldn't let him touch it.

"Swim", "touch", "hello", "goodbye" and "help".

 The last Sukuna only learned because he tried to move to a nearby pool and got stuck halfway between two rocks.

"Careful."

Fortunately, Yuji soon arrived, repeating the word as he helped Sukuna return.

Yuji laughed when Sukuna first grabbed his foot and squeezed his toes, struggling to stay still while the merman curiously explored his strange legs. However, he couldn't see anything under the uncomfortable clothes, so he left it at that.

But Yuji wanted to explore in return. Fair was fair.

Sukuna slowly emerged from the water and went to the nearby rocks, its elegant black tail swaying a few times as it lay on its stomach and looked at Yuji. The human stared open-mouthed at its flippers, its hands raised shyly. It glanced at Sukuna's face before reaching out to touch it.

The merman let him explore; his fingertips traced the bright red scales and briefly brushed against the spiny fins, whispering to himself, things Sukuna didn't care about. However, he was most fascinated by the tail fin, his palm spreading across the thin membrane. Sukuna glanced briefly at Yuji before suddenly wiggling his tail, slapping the human's cheek and eliciting a yelp from him.

"You're too funny for someone who always makes a face."

 Sukuna replied softly, amused, while Yuji stammered and wiped his face disdainfully. If only all humans were like him.

 Unfortunately, they weren't.

Sukuna discovered this late at night when he heard footsteps approaching. It was very strange. Yuji usually came during the day. And there were many footsteps, many humans. He didn't trust it at all. A wise decision, but one that didn't allow him to escape his destiny.

The humans were stupid enough to jump straight into the rock pool without looking, laughing and splashing. Sukuna remained hidden in the darkness, out of sight. He counted four humans in total. Then one of their feet brushed against his tail, provoking a startled cry and frantic movements as they hurriedly escaped the water. 

Damn, they knew he was there...?

One of the humans shone his phone into the pool. Sukuna couldn't avoid the angle. He vaguely heard them talking above the water, their voices growing louder. Then someone threw a rock. With his teeth bared, Sukuna emerged from his hiding place and lunged out of the water toward them, provoking more screams and panic.

Another stone was thrown at him.

This hit him on the side, eliciting a hiss and a growl from the creature as it lunged forward, narrowly missing the ankle of a nearby boy. That's it. Now he could return the favor. Sukuna returned to the water as the humans frantically escaped, leaving him in peace.

But not for long.

Not even an hour later, the same four returned, immediately throwing stones into the water until Sukuna growled and swam towards them. This time they were armed.

The moment he emerged from the water, something resembling a fishing rod struck him on the head. Sukuna was startled, shocked for two seconds, before quickly dodging a second blow, grabbing the wooden weapon and trying to move it out of the girl's reach. However, four against one, he couldn't avoid the metal swinging across his face, cutting his right eye and forehead.

Growling with a sharp pain, Sukuna turned and managed to sink his claws into the idiot's leg, dragging him to the ground as he tried to pull him towards the rocky pool, where he had the advantage.

The friends of that hideous thing wouldn't let that happen, immediately striking Sukuna's hands. The delicate membrane between his fingers tore, but it was the gleaming metal weapon that caused the most damage, completely severing two of Sukuna's fingers and drawing a blood-curdling scream from his wild lips. Despite this, it released the human; it pulled him underwater.

Down below, the humans couldn't move quickly, nor breathe; they thrashed frantically. It was all too easy for Sukuna to disarm him and attack his throat, sinking his needle-like teeth in and tearing out his jugular vein, blood splattering into the water. The rich, iron-rich taste made Sukuna want to vomit. The other cowardly humans ran, abandoning their dying friend as Sukuna released the spasming corpse and retreated back into hiding.

 He hoped Yuji wouldn't get upset, that he wouldn't leave him. He was just protecting himself from those damned, annoying, smelly humans. They were nothing like his Yuji, who was good and smelled wonderful, exuding peace and comfort.

He heard more footsteps, many more than before. Countless. Good heavens, was it a giant crowd of humans now? Had they all come to kill him? He couldn't even count the number of heads peering over the edge of the rocky pool, their lips twisting into mocking grins as they growled, leaning against the jagged rock walls. He saw a series of strange man-made devices in their hands, heard the hum and vibration underwater. No rocks, at least.

Then something shot through the water, embedding itself in Sukuna's tail.

The merman hissed and ripped off the small metal object, grimacing. Okay, that wasn't friendly. Sukuna didn't hesitate to attack the surface again, heading towards the nearest human. They seemed to expect this, hastily retreating to a safe distance that Sukuna couldn't follow.

He returned to the water, pushing the stiff corpse aside.

But as he hovered above the sandy ground, his vision blurred as he felt a sting, struggling to maintain focus. His limbs seemed sluggish, responding more slowly, lagging behind. Sukuna grumbled, half-closing his eyes at the brave human watching him from above. 

What did they do to him? Poison? Did that thing poison him before?

He imagined that was exactly what happened when his body began to refuse to obey him, falling to its resting place at the bottom of the rocky pool. Perhaps that was where he would truly die, but instead of starvation, he would be killed by those frustrating and abominable humans who wouldn't leave him in peace!

...

The next time Sukuna woke up, the water was clean, fresh, and more refreshing than the ocean itself. He felt the soft sand under his fingers. Well, under which fingers he still had... When his only good eye blinked and opened, he recognized nothing.

From a distance via... humans. Standing. In the water? What...?

Sukuna blinked slowly, reaching out to carefully touch his injured eye. He knew it should hurt, but it didn't; he couldn't feel the pain. Those humans... 

A flash of bright white light came, and Sukuna boiled in response. He glared and watched as one human reprimanded another for fiddling with their phone. But how were they underwater like that?

Cautiously, he swished his heavy tail and emerged from the small cave.

Only then did he realize that it wasn't just a small group of humans—he was completely surrounded by them, all with phones in their hands or smiling at him. Was he back in the ocean? And... were the humans there with him? How? Were they helping? But when he tried to swim over the humans, he immediately encountered resistance, bumping his head on something.

He heard laughter from downstairs.

Sukuna shuddered and reached out, his palms smoothing over an invisible barrier. He remembered hearing about it, about " glass ."

Wait... Sukuna turned to the side, his hand tracing the surface of the glass as it followed its curve, hisbrow deepening as he circled back to where he had begun.

I wasn't in the ocean.

I was trapped in a fake ocean surrounded by glass.

When he swam to the surface, his head appearing above the water, he found himself surrounded by synthetic lights in a large room, and a collection of humans along the water's edge, exulting with excitement at his appearance.

It was their pet, kept in captivity in a larger, more sophisticated rock pool.

Sukuna grimaced and dove back into the water, briefly exploring the small habitat he'd been placed in. Thick, thriving algae grew in abundance beside a shallow, rocky cave lined with coral. And if he looked closely, he could see some tiny creatures crawling around. Shit. Did they want a pet?

 Sure. Not that Sukuna could escape. But it wouldn't make things easy for them.

It went back to the cave and hid, wagging its tail and covering most of the entrance, blocking itself from view. The humans could go fuck themselves, look at something else.

Even when he heard the sound of water above and vaguely made out the word " fish " being spoken, Sukuna refused to follow the sounds. He wouldn't give them that satisfaction, he wouldn't give them a damn thing. However, when the lights dimmed and grew dark, the humans disappeared.

 Realizing it was the right moment, Sukuna emerged from his hiding place; he followed the scent of food through the water and found a small stash of three fish washed up at the bottom of the tank. Well, at least they wouldn't let him go hungry, that was good to know. And now that he was alone, he could explore freely. Behind the glass there seemed to be air, no water. It made sense now why humans could be there and not drown.

In the distance, he could see some other glass tanks, smaller than his, but containing fish and even some jellyfish and octopuses. They kept ocean creatures as pets, to walk around and admire. Humans were certainly strange creatures, if that's what they did with their time instead of hunting or staying with their families.

But the moment the lights came back on, Sukuna retreated to his cave. More splashing, more promises of fish , but Sukuna ignored them, hiding a low growl. They gave up relatively quickly, allowing him to rest and relax for a while until the humans started coming in, phones in hand, pointing, shouting, and banging on the glass. This was too annoying...

Then he heard a very familiar voice shout: "SUKUNA!"

The merman felt his heart beat faster and he perked up. His good eye widened as he emerged from the cave, searching his surroundings. There, he pushed his way through the crowd and banged his fist on the glass. It was Yuji. Sukuna immediately swam closer to his human.

Although they were separated by glass, there was no doubt that it was Yuji, with tears in the boy's eyes as he laughed and said something, and then said his name again.

"Yujjji," Sukuna replied, ignoring the shocked humans chatting nearby with their phones raised.

Your human was there!

Yuji smiled and tapped lightly on the glass, his palm spread across it as he spoke. Sukuna didn't understand anything, but when he heard his name, "Sukuna," the merman hissed in response, his ears widening as his tail wagged to the side.

Without explanation, Yuji turned and left. 

Sukuna tapped his tail against the glass, hissing softly, but watched as Yuji went to speak to someone else, pointing and gesturing. His human waved to him, said something Sukuna didn't understand, and followed the other through a door, disappearing from sight. Sukuna grimaced. He immediately returned to his cave, hiding again.

Yuji wouldn't leave him like that. He would do something, talk to the other humans. Maybe try to free him? Free him in the real ocean instead of that small, fake one? He hadn't left for more than a few minutes before hearing those annoying humans splashing overhead again. Sukuna intended to ignore them until he heard:

 "Sukunaaa!"

He emerged from the cave before he knew it, swimming immediately toward the owner of the voice. This time, as he surged forward, Sukuna didn't bother to slow down when he broke the surface, colliding with Yuji and knocking the boy onto his back, eliciting a cry from him. The merman didn't hesitate to press his face against the other's cheek in greeting, as he used to do with his old friends.

Yuji laughed and patted him back, saying, "Hello, Sukuna, hello, yes, hello." Simple words that Sukuna knew.

He tried to reproduce the sounds, but they came out confused: "hello, Yujj, 'llou, 'oll." His poor throat ached as he spoke many human nonsensical words, returning to singing. However, hearing whispers nearby, Sukuna stiffened and sat up more, looking at the blue-eyed human close by, a growl slowly echoing in his chest.

"No, no, Sukuna, no!" Yuji hurried to say, squeezing the merman's arm until he stopped growling. "Help. He'll help Sukuna."

"Help?" Sukuna scoffed, backing away until he was in the water, his head above the surface at the edge of the tank. Did he mean that those humans had captured and locked him up to help him? Yes, no, that was a load of nonsense! Even so, Sukuna didn't disappear, staying close to Yuji. He didn't understand everything they started discussing, occasionally hearing his name mixed in, but without context.

Sukuna simply grumbled and grabbed Yuji's clothes from his legs, using them to drag the human closer, despite the difficulty. He wouldn't let the brat go again. In any case, the masculine-looking human eventually nodded and left the room, leaving only Yuji and that other human who wouldn't stop smiling at him.

"Gojoooo," Yuji said, pointing at the person. Sukuna squinted. "Gojo, Gojjjjooo."

Was that his name? Was he learning more names?

The name came out confusing, more like "Gjoo," but it made them smile and laugh, clapping and making Sukuna's ears twitch with the high-pitched sound.

Fortunately, Yuji made him stop. Sukuna couldn't be more grateful to the boy. However, he was more than a little surprised when Yuji removed the outer layers of his clothing and said something to Gojo that made him leave, shouting the same thing Yuji used to do when he would return soon.

Then Yuji jumped into the water with an excited shout.

Sukuna swam behind his human as he briefly dove into the water, very slowly and creating many bubbles and splashes. Humans really weren't made for water.

Fortunately, Sukuna does.

He waited until Yuji was above the surface, smiling and snorting, before saying: 

"I'll help Yujjiii."

When he offered his hand, Yuji smiled and eagerly took it, allowing the merman to drag him underwater, past the glass barrier. Sukuna checked on the boy, watching him squint and hold his breath as he was pulled, looking around curiously. Not wanting to test his lung capacity, Sukuna brought him back to the surface a moment later, allowing him to take a breath before demanding to go again.

It was the most interaction the humans had ever seen from him up to that point. And when Yuji left, he left too. Sukuna refused to eat any fish offered directly by humans, unless Yuji gave it to him. Otherwise, they would have to wait until they left before the merman caught them. And, sure enough, Yuji returned every day to spend time with him, teaching and learning.

Although Sukuna didn't particularly like the sharp metal that Gojo brought, Yuji convinced him that it was meant to help, and that everything was fine.

 "A minor injury," Yuji explained, touching his own face and pointing to it.

"Small? Okay."

Sukuna still bared his teeth and growled when the human pierced him with the tiny metal rod, though it hardly hurt.

When Sukuna learned to speak, he only knew enough of his own language to ask: 

"Suku, don't go away, why?" 

Yuji struggled to find an answer until, finally, he grasped Sukuna's hand and touched the missing fingers. He traced along the torn web. He stroked his cheek and his scarred right eye.

 "Sukuna is injured."

It hurt even more to hear the truth; he didn't want to hear it. He was too injured to return to the ocean and survive. He was slower than usual, found it harder to turn without gills, and only had one eye.

Sukuna would never leave that place.

He grumbled at the revelation, gave a small nod, and chose to rest on the edge of the tank while Yuji tried to comfort him, running his fingers over the horns and sensitive fins. At least he wasn't alone, and those humans seemed relatively nice, despite the needles. And Yuji... didn't want the human to leave anymore. 

Couldn't he have stayed there? Sleeped nearby? Why did he have to sleep somewhere else, leaving him alone in that isolated tank while strangers stared and gaped at him?

No. Yuji would keep it now; it belonged to Sukuna.

It was simply... a matter of communication. Or rather, struggling to overcome the communication barrier between them. When Sukuna brought their faces together as he usually did in a greeting, the human simply laughed and hugged him back, murmuring something and his name.

As the merman slid out of the water and lay atop the human, pinning him down on his back, Yuji stood still, blinking at Sukuna and tilting his head. He made those sounds that meant he was confused by what the sea creature was doing. Sukuna couldn't tell, he didn't know the words. Humans didn't have gills for him to nibble and transmit his connection, but when it moved down and briefly scraped its teeth against Yuji's neck, his breath caught in his throat and he winced, recoiling quickly but still holding Sukuna, his eyes wide as he examined the merman's face.

"What is Sukuna doing?"

Upon hearing the question, the newt let out a low cry in response before twisting his tail to the side. Hidden among dark scales in front, his penis in its slit became more prominent, with sticky fluids leaking out.

He would make Yuji his companion, so he couldn't leave.

An exciting scent of pheromones hung in the air. Yuji didn't exactly flee, but he stood up with trembling feet, despite Sukuna's disgruntled grumbling, promising to return when he escaped. His face was tinged with a peculiar layer of red, and the human stepped back and quickly exited through the door.

Well, that was a disaster.

Sukuna went back into the water, dove down to stay wet before opting to wait on the surface, staring at the door. Yuji said he'd be back... Unfortunately, it took almost an hour for Yuji to return with Gojo nearby. Well, he wasn't leaving him yet.

"So he's an alpha?"

"Yes."

"And do you want to mate?"

"Yes."

But the moment Yuji sat down with his feet in the water, Sukuna stood up again, persistently pressing his face against Yuji's neck and trying to lay him down again to claim him. However, when the young man pushed against his chest, the merman leaned back, his eyebrows lowering. What's the problem?

"Wait," Yuji said, glancing sideways at Gojo. Sukuna followed his gaze, still confused but listening.  Okay... waiting... for how long? I didn't want Yuji to leave at night! But the human avoided further advances, repeating: 

"Wait, Sukuna, wait!"

For God's sake! Damn it. If Yuji wanted to wait any longer, he could wait longer. The merman recoiled with an irritated snort as he dove into the water and then waited, but one of his arms slipped between Yuji's legs as he looked at Gojo. It probably had something to do with that human, who was so busy writing something...

"You can, but I need you to sign this."

The day continued like any other, with Yuji teaching him a few new words and then swimming with him, allowing Sukuna to pull him underwater a few times before they rested. He didn't find it funny when Gojo tried to get him to retrieve toys that sank in the water. However, just like every other time, when the people below began to dwindle and disappear, Yuji got out of the water, dried himself off, and left.

Sukuna hissed, a low, deep sound of sadness.

Instead of the usual goodbye, Yuji gave him a strange look and said, "Sukuna, wait."

Oh?

His human disappeared with Gojo outside the room, leaving Sukuna alone, as always. But this time he knew Yuji would return. He had told him to wait, that he wouldn't leave for the rest of the night. And, sure enough, an hour later, Yuji and Gojo returned.

"Yuji, for your safety I need to keep an eye on Sukuna, even if it's embarrassing for you."

Sukuna heard them exchanging strange words, only understanding a few things. Gojo sat to the side, holding a larger version of the phone in his hand, pointing it at them.

Yuji intentionally ignored his fellow man as he approached. "Hello, Sukuna," he greeted, as always. Sukuna returned the greeting, but instead of sitting down, Yuji remained standing awkwardly.

Sukuna let out a low hiss, drenched himself in the water, only to resurface in time to see Yuji grab his clothes and begin to remove them. Emerging further from the water, curious red eyes scanned the exposed skin, absorbing everything. He knew humans didn't have tails, but his head couldn't help but tilt curiously at the sight of Yuji's penis, and even more so at the familiar cleft between his human's legs. Well, at least it wasn't too different from what his species had, right?

But when Sukuna sniffed the air, he realized it wasn't the same. It smelled like an omega mermaid, but much more appetizing than before when they met. Then, the instant Yuji sat on the edge of the tank, Sukuna crawled out of the water, leaving his human motionless.

With slow movements, the merman reached out to gently poke Yuji's leg, pushing it further to the side while peeking at the hard thing that looked like his penis—it had small pink hairs on top, and below it, where most of the smell came from, an opening. How strange.

The young man didn't stop him from approaching, sniffing, and even trying to pull Yuji closer to the water, into a more comfortable position. His human let out that strange little laugh he gave when he didn't know what to do or say. 

Sukuna's cute companion...

Sukuna made it obvious what he was doing as he settled between Yuji's legs, his arms crossed over the human's thighs while his fingers danced over his hips and back, gazing into his bright golden eyes.

"Is Sukuna alright?" he asked, his voice breathless.

The merman snorted. "Yes, fine." Silly thing.

Yuji smiled and nodded, gently running his fingers through Sukuna's hair, briefly playing with his horns. "Yes, Yuji, everything's fine too."

That was all the reassurance Sukuna needed before pressing his face against the precious cleft between Yuji's legs, his forked tongue snaking out to explore. Immediately, his human shuddered in surprise, a muffled moan filling his ears, but he didn't try to escape or push Sukuna away. He interpreted it as encouragement, dragging his tongue from bottom to top, savoring the delicious taste.

Yuji's legs trembled at the end when he hit a specific spot. Hmm...

Without rushing, Sukuna repeated the action and was rewarded with a sweet, soft, panting moan. Such beautiful sounds.

"Is everything alright there, Yuji?"

Then Gojo spoke, asking something. Sukuna didn't know what, but the cadence of his words at the end revealed it was a question. Fuck off, annoying human. More irritating, however, was the fact that Yuji answered him, replying despite his eyes remaining fixed on Sukuna, his legs trembling as Sukuna added more pressure, stumbling over his words.

Well, your attention should be focused solely on him, and only on him, your beautiful companion...

And when Sukuna raised his mouth to the erect penis with its pink and inviting tip, he didn't hesitate to seal his lips around Yuji and take it all in, sucking hungrily and precisely, provoking a sharp cry as his fingers gripped Sukuna's horns, squeezing and pulling lightly, drawing him closer.

And who was he to deny his beautiful companion the pleasure he deserved? He had cared for Sukuna for a long time, bringing him food and then keeping him company so he wouldn't lose his mind. He deserved a little treat.

"Isn't he hurting you? I've heard that mermaids have rough tongues."

Gojo spoke again. Sukuna suppressed the urge to growl in response.

He pulled his mouth away to descend again to Yuji's pink opening, from which a clear, viscous liquid flowed. He spared no effort when their lips made contact. This time, however, Yuji couldn't even formulate a response to Gojo, groaning as he fell back onto the floor, one knee bending as his hips rolled, trying to push Sukuna's tongue further inside while the merman sucked on his main protrusion.

Your human was startled once again.

And despite the obvious biological differences, it wasn't so difficult to tell exactly when Yuji came: white jets shooting from his penis, his thighs trembling as his head tilted back, panting and moaning, his back arching off the floor.

Sukuna continued to fuck him with his tongue, a low rumble vibrating inside his chest.

And when he finally calmed down, panting and limp on the wet floor, Sukuna withdrew his tongue and took a look at that slippery slit. A considerable amount of white liquid came out, so he could only assume that Yuji was a receptacle, made to generate offspring, not like an alpha that fertilized them, unless human biology was even more complicated.

In any case, that was enough to confirm what he most wanted to know. Sukuna felt his own interest slipping away, eager to taste that same warm heat he had just felt around his tongue.

But when he was completely out of the water, Gojo said something louder.

Yuji placed his hand on Sukuna's chest as he said, "Wait, wait..."

What were you expecting this time?

Sukuna hissed, but listened, instead leaning in to nibble at Yuji's neck. The boy groaned, a wrinkle forming on his forehead at the thought of being strange. Right, his own biology must be strange to him too. So he let Yuji satisfy himself, leaning back and allowing his human to climb onto his lap and timidly reach towards his two penises that emerged from the tail slit, coiled around each other. The moment Yuji's fingertips made contact, Sukuna let out a few moans, reacting and responding, enveloped by Yuji's hand.

With a breathless, airy laugh, Yuji's fingers rubbed against its slippery, grooved surface. Sukuna couldn't stop the low, satisfied sound that started in his chest, even as Yuji spoke to Gojo, saying something he didn't quite understand. Should he tell him what was happening, perhaps?

He didn't mind anyway, especially when Yuji tightened his grip. The merman let out a sharp growl in response, his weight closing in as he pressed his face against Yuji's neck and bit a little harder, gripping his human's waist. 

Come on, let them in, darling...

"Really, you two won't have any problems mating."

"And can we be together?"

Yuji said something else to Gojo, to which the researcher replied:  "Yes!"

That seemed to be enough for Yuji to sigh and lie down, wrapping his arm around Sukuna's waist and pulling the merman closer, smiling at him, receiving a smile in return.

Yes, perfect, finally making it all yours, never to be separated again.

Sukuna didn't hesitate to bring their bodies together. A low rumble vibrated between them as he lay atop Yuji, the weight of his tail pressing lightly against the human's thighs to hold him in place. Normally, mating would be easier in the water—fluid, natural, with the currents aiding movement—but humans needed air to breathe. So this dry position, on the cold, wet bottom of the tank's edge, seemed the best option they had.

He spread Yuji's legs wide, welcoming him with his clawed hands tracing the warm, tanned skin. He nibbled and kissed the human's neck, feeling the accelerated pulse beneath his forked tongue. Their two penises, now free of the opening and entwined, explored curiously: probing different areas, brushing against the moist entrance, testing the resistance of the soft flesh. When they finally found the point that yielded, Sukuna pushed slowly. The first slid inside with a wet, low sound, stretching Yuji more than any tongue ever could.

Yuji gasped loudly, his whole body trembling beneath him. His hands gripped Sukuna's horns tightly, not to push them away, but to anchor themselves. Sukuna blocked out any sound Gojo might be making in the background—it didn't matter. The world now consisted of the tight heat enveloping him, the sweet, musky scent rising from Yuji's skin, the way the human's chest rose and fell too quickly. The stiff, contorted tentacle slid deeper, settling completely inside his mate's hole. Sukuna purred softly, satisfied, feeling the inner walls contract around him as if trying to pull him even further in. He would carry all his descendants there. Yuji would be the perfect mother for them.

However, the moment the second penis began to probe the already occupied entrance, pressing against the first, Yuji suddenly stiffened and hissed through his teeth.

Sukuna frowned, annoyed. He placed small bites on Yuji's neck and shoulder, licking the red marks he left, trying to distract him. Humans didn't have gills for him to nibble and stimulate like he would a mermaid; he couldn't vibrate there to relax his partner's body. So he used what he had: a rough tongue brushing against the collarbone, claws tracing light circles on the thighs. The rest of his tail wrapped around Yuji's leg to keep him open.

Slowly, very slowly, the second penis began to force its way in. Yuji whimpered loudly, his legs instinctively lifting, spreading even wider as he struggled to accommodate the thick circumference. His face contorted in a mixture of pain and something deeper, more confused.

"It hurts..."

The voice came out weak, trembling. Sukuna chirped in response—a low, almost comforting sound—licking Yuji's sweat-dampened cheek and pressing their faces together. Sweet companion. Doing so much good for him. Welcoming him so well in their first mating. 

There would be many more after that; each one would be easier, more natural, Yuji's body molding itself to him over time. When their hips finally aligned completely, Yuji's feet hooked behind the base of Sukuna's tail, and the human shuddered violently. Sukuna enveloped Yuji's erect penis with his right hand—his webbed fingers sliding across the sensitive skin—and the movement elicited a quicker, more desperate gasp.

For now, Sukuna kept their bodies pressed together, feeling the warm tension coiling inside him, the pressure slowly building as he showered Yuji with affection: long licks on the neck, gentle nibbles on the ear, deep purrs that vibrated through his chest and made Yuji tremble in a different way. Distracting him from the uncomfortable fullness. Preparing him for what was to come.

And it was about to get much more crowded.

Now...

The first egg began to descend. Sukuna grunted sharply, his abdominal muscles contracting as he struggled to push it through Yuji's tight entrance. The pressure was almost overwhelming—round, firm, insistent—and Yuji tensed again, his eyes wide.

"Teacher, something's going in..."

Sukuna heard the footsteps approaching. He growled softly, glaring at the approaching researcher, but he didn't stop. He couldn't stop.

"I think they're eggs," Gojo said, his voice too calm for Sukuna's liking. "He wants you to bear his offspring."

"Oh my God."

"Yes, Yuji, he wants you to be the mother of his babies. Isn't that wonderful?" His voice shifted from interested to cheerful before he returned to his notes.

"B-But won't that be a problem?" Yuji's voice trembled, full of doubt.

"I don't think so. His body was made to reproduce, so it's like he's his alpha merman...in fact, that's what it is."

Sukuna was fed up with that strange conversation. He tightened his grip on his hips, pushing and demonstrating his dominance. The egg finally passed, sliding inside with a deep, wet sound, settling into Yuji's belly, who opened his mouth and threw his head back, moaning. Sukuna purred contentedly, his tail wagging and lightly tapping the ground.

But it didn't stop there. A second one was already on its way, eager to join its brother.

Yuji whimpered with each movement, trembling all over, avoiding Gojo's gaze as he clung to Sukuna, hiding his face in the merman's shoulder. His clawed hands gently traced the tanned skin, moving up his back, down his sides, calming him. Sukuna growled softly, grunting with the effort of each egg being laid—they were slow, large, made to last. 

When the pressure shifted inside his intestines, Sukuna writhed and tilted his head to the other side, striking the left side of Yuji's neck. The human let out a curious buzzing sound, only to shudder violently as the teeth sank deep into the soft flesh. The moans turned into muffled cries, which startled the alpha teacher, causing him to leap forward.

Firm hands tugged at Sukuna's hair and horns, trying to push him away while the blue-eyed human screamed frantically, watching the blood trickle from Yuji's neck in hot rivulets. But Sukuna ignored the idiot's anguish, for it was part of mating. He closed his eyes and felt the second penis release—a hot, thick load, flooding Yuji's insides, fertilizing the eggs that were already there.

With his tongue hanging out in spasms, Yuji writhed beneath him, his heels slapping against his tail a few times, but he couldn't do anything but hold on tighter as Sukuna pinned him in place, filling his hole with an unbelievable amount of semen. Yuji's belly swelled slightly under the pressure, visibly rounding out.

"That's it, Yuji," Gojo said, finally giving up on interfering, only squeezing the boy's hand to comfort him—much to Sukuna's deep dismay. "You'll be alright."

When the last small drips disappeared, allowing Sukuna to set aside his most urgent wild instincts, the merman slowly pulled out his teeth and licked the wound in long, careful apologies, murmuring hoarsely: 

"Yuji, it's okay. Yuji is fine."

He could see the tears in his companion's eyes: satisfied, confused, and breathless. 

Gojo spoke again, his voice lower, calmer. Whatever they said must have worked, because Yuji gradually calmed down, sighing deeply and closing his eyes as he gently ran his fingers through Sukuna's hair, allowing the merman to continue cleaning the bite mark he had left behind—now a red, swollen mark of possession.

When their penises finally retracted, slipping out with a wet sound, Yuji whimpered softly, lowering his hand to touch the sticky fluids that slowly trickled from his flushed, reddened hole. Gojo approached, circling to get a better look, while Sukuna plunged into the water to avoid drying out.

But upon spotting an egg about to escape from inside Yuji, Sukuna growled loudly, his teeth bared.

Yuji startled and quickly covered the crack with his hand, holding the egg in place so it wouldn't fall. Sukuna calmed down instantly, crawling out of the tank again and intentionally lying on Yuji's strong, handsome chest, playing with the sweat-damp pink hair while purring softly. He didn't like the way Gojo snooped, poked, and explored with cold instruments, but he knew human ways well: they were curious, eager to learn. And Yuji didn't seem to be leaving anytime soon—not while carrying such a precious burden inside him.

Certainly, after mating, Yuji wouldn't abandon him so easily. He would spend the nights sleeping within Sukuna's sight, even if not in the water. And Sukuna would remain vigilant. Always.

Because now Yuji belonged to him. Completely, irreversibly, to him.

The researchers were curious and perplexed, continuing to ask questions and "investigate" Yuji all the while, despite Sukuna's low growls.

But whatever happened, Sukuna knew one thing for sure: he would never lose Yuji again, he would never be separated from his perfect little human.

The puppies would be born, grow up, and become strong. And he swore silently, he would get them all out of there. All together. Even if it meant killing all the bespectacled heads there.

...

Months passed in the fake glass tank, and Sukuna learned to hate the prison even more—but he tolerated it because Yuji stayed there almost every night, sleeping on the edge or on an improvised bed that Gojo had brought, always in sight. Yuji's belly swelled slowly at first, then visibly rounded out, carrying the eggs that Sukuna had deposited in it. The merman spent hours with his face pressed against the human's belly, listening to the multiple heartbeats, purring softly as he licked the stretched skin. 

"My cubs," he murmured possessively. "They will be strong. Like me."

Yuji smiled every time, even when his back ached or when the researchers poked him with cold instruments. "They're going to be beautiful," he'd say, running his fingers over Sukuna's horns. Gojo watched from afar, taking notes, but Sukuna growled whenever the blue-eyed human got too close. No one touched Yuji without permission.

The eggs didn't hatch all at once like in ordinary mermaids. They remained inside Yuji for weeks, growing, until the human's body began to expel small, translucent sacs—smaller eggs, protected by a gelatinous membrane. Sukuna picked them up with extreme care, using his claws so as not to tear them, and deposited them at the bottom of the tank, among the thick algae and artificial coral. He covered them with fine sand and algae, watching over them day and night. Yuji dove whenever he could, helping to tidy up the makeshift nest. 

"Be careful, Sukuna, they are fragile."

He always warned him when going up and Sukuna would snort.

 "Fragile? They're mine. Nothing breaks them." His sentences were getting better and better, demonstrating his thoughts and his way of speaking more clearly.

Then came the night of the hatching.

The artificial lights in the room dimmed as usual, the humans had left, leaving only the faint glow of the emergency lights. Sukuna floated in the center of the tank, his tail protectively wrapped around the nest. Yuji slept on the edge, one hand dangling in the water, lightly touching the algae.

A subtle tremor came. And then another.

Sukuna raised his head, crimson eyes gleaming in the dim light. One of the eggs pulsed—the membrane stretched, cracked slowly. A low sound, like shell breaking under pressure. Another egg trembled. And another.

He swam closer, his heart pounding—something he rarely felt. " Come, little ones ," he murmured, his voice bubbling in the water. " Come out..."

The first egg cracked open with a soft snap. A small tail, black like his but with soft pink stripes, emerged first. Then came the tiny body: pale skin with fine, shiny scales, short, rounded horns still soft, delicate fins that trembled at the touch of water. Golden eyes opened—just like Yuji's—blinking confusedly. The hatchling gurgled, a high-pitched, hungry sound, and swam awkwardly toward the surface, followed by others.

Yuji woke up to the gurgling. He sat up quickly, his eyes wide. "Sukuna...?"

The merman lifted them one by one to the edge, letting them float near Yuji, who was already eagerly entering the water. "They're born," he said, his voice low and proud. "Look."

As soon as the pups caught Omega's familiar scent, they swam straight to him, clinging to his clothes and exposed skin as if they instinctively knew: their mother was there. One curled up on the human's arm, another gently nibbled at his finger, and the other three floated around, chirping and seeking contact. 

'Your mom,' Sukuna thought, satisfied. 'They know.'

Yuji chuckled softly, touching them carefully as he saw that they were smaller than normal human babies and, apparently, quite conscious. But suddenly he frowned and lowered his gaze to his own chest, worse than in previous days. Something damp seeped through his thin shirt, staining the fabric and mixing with the water. 

"What...?" he murmured, confused, pulling up his shirt and placing his hand there.

Sukuna swam closer at that very moment, gently extending its claw to touch the spot. It licked its damp finger, tasting the sweet, nutritious liquid. " Food ," it purred. "For the pups. Your body knows what's good for them."

Yuji blushed intensely, his eyes wide with embarrassment. "Out of nowhere? My body... I did feel it hurting here from time to time. This is strange..." 

He stammered awkwardly, pulling down his clothes, looking around as if expecting someone to see, even though they were alone. All omegas did this, but he thought it would be different for him. 

But the puppies didn't wait for explanations. The first one snuggled against Yuji's chest, instinctively searching for the swollen nipple through his shirt. Reaching underneath, it began to suckle with satisfied squeaks. Another joined in, occupying the other side and being embraced by Yuji. When the first two had finished and floated back into the water, they yawned, swimming lazily; Yuji removed his clothes, resigned to the fact that he would have to get used to it. If the teacher saw, he would go crazy.

Immediately, two other puppies took their place, clinging to each other and nursing with voracious hunger. Yuji held them gently, still red-faced and embarrassed, but with a soft smile on his lips. 

"They are voracious... just like you, Sukuna."

The newt watched, a steady purring in his chest. As the seconds drifted away, the last pup—the smallest, with crimson eyes like his own—snuggled onto his free breast, nursing alone while the other side remained empty, still leaking a little sweet milk into the water.

Sukuna dove in and watched closely; he felt his mouth water. The smell was tempting, familiar, and an instinctive part of him wanted to lean in and taste it too—to lick, to suck, to share that moment as something intimate between companions. But he restrained himself. Not now, not with the pups there, and not with Yuji still embarrassed. Better later, alone, when he could explore slowly, savoring the new food his companion had to offer.

 ' Mine ,' he thought, licking his lips. 'For me later.'

The pups, satiated, chirped and swam in circles around them, exploring the tank with childlike curiosity. One tried to bite the glass, another clung to Sukuna's tail, and the smallest remained in Yuji's arms as if seeking comfort and security.

Gojo showed up the next morning—as always, with his phone in hand and an irritating grin. But he stopped when he saw the scene: Sukuna floating with the puppies nestled against him, Yuji sitting on the edge with two in his lap, all wet and happy.

"Look," Gojo said in a low voice. "Now you have a complete family, your dream has come true."

Sukuna growled, but did not attack. The puppies looked at the strange human, curious, their voices trembling slightly.

"Thank you, teacher." Yuji smiled at Gojo. "They hatched last night. They're perfect."

"No needles, no experiments." Sukuna pressed Yuji against him possessively. "They're ours..."

And for the first time since being captured, Sukuna felt far more hatred for the glass tank. Because there, surrounded by Yuji and the pups who carried both their blood, the artificial ocean seemed... enough. For now, he couldn't allow himself to be accepted solely for the safety of his family.

After a few minutes of idle chatter, the teacher watched Yuji emerge from under the warm blanket, enter the water, and dry off for a few moments to regain warmth. He became uneasy seeing their children grumbling and Yuji immediately jumping into the water to soothe them; it was visual torture. Then he coughed, looking away.

"Actually, I came because I have good news." The man removed his sunglasses, letting the evidence of his blue eyes convey confidence. "I built an aquarium connecting my house to the ocean and... I'm going to let you live there."

"WHAT?" Yuji shouted, his voice muffled as he patted the backs of the children who were now huddled around him, being breastfed again. "How?"

"Get out of here?" Sukuna wrapped himself around Yuji and the children, rubbing his face against them.

"Yes... Sukuna will have access to go to the sea whenever he wants, and Yuji to the surface, but their children... it would be a risk for them to go to the sea right now." Gojo bent down, trying to touch one of the newborns' heads for a second, managing to do so before Sukuna's hand could stop him. "Don't misunderstand me, I have plenty of money and my house is very large. Doing any experiments will only be a hobby, and only if you allow it."

"Would you do that?"

Sukuna saw Yuji's eyes well up with tears and a gleam of hope, and he heard Gojo explain something about using influence to easily erase evidence of their existence, and how he had become attached to them, like a friend. He saw that Yuji was holding back from leaving to thank them, but he restrained himself, letting tears fall from his eyes in a sob.

"Yuji is happy now, and Sukuna is too." 

In a comforting gesture, he licked away his beloved's tears, embracing him and kissing his lips, tasting the salty flavor in the mouth that now smiled at him. Then he turned his eyes to the man's blue ones, unable to help but smile himself, knowing that the wretch was truly a good person; he had learned to like him, despite him being a strange alpha.

"Do it."

With a smile, Gojo extended his hand, which he quickly understood was for a handshake, like some kind of greeting he'd seen the other humans use among themselves there through the glass. Their hands clasped in agreement, and Sukuna thought that if he had privacy with Yuji and his cubs, 

before Gojo stood up and adjusted his jacket.

"Consider yourselves free tomorrow, I'll take care of everything. Friends."

END

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