Chapter Text
Katsuki swam with small, energy-conserving sways of his tail above the sandy floor, red eyes sharp for motion and disturbances. He kept his fins narrow and snug along his body, reducing drag and hiding his attention-grabbing colors as much as possible.
He did not blend in here on the sandy floor, a gently sloping plain of beige broken by few stones and sea grass patches. Katsuki, with his sun-kissed skin and brightly banded tail of pale yellow and bold orange and black stripes stood out. When his spiny, feathery-like fins were spread, the red eye patterns surrounded in burnt orange and white contrasted far too obviously, and not all predators would be dissuaded from any aggressive displays he made, nor be put off by the venom in his barbs. Even the volcanic glass knife by the narrow satchel hanging off his shoulder would help him little against something willing to eat merfolk if caught by surprise.
Being blessed with lion fish features did afford him some audacity, though, and Katsuki had brawled with far bigger merfolk and a number of predators to protect his pod before. Which was why no one could dissuade him from leaving his birth shore and its safer fringe reef behind.
Katsuki hungered for something new… something else. He possessed an aggressive streak, so when he reached maturity, many weren’t surprised that he wanted his own territory. He thought that might be it, just control over his own domain, having a right to fight any and all rivals as he pleased. His agitation and restlessness wouldn’t allow him to remain with the weaker shore merfolk. For the past two weeks he’d dared across the open expanses for new reefs. Hoping blindly to satisfy the nameless hunger in himself.
He’d felt the change in current that indicated a body of land yesterday. Slight, barely there, but something that changed the flow of water. After a restless night sleeping buried in the sand again, which he did not like doing, he’d followed the change and promising trace scents, encouraged by the semi-regular flight of birds overhead.
Hopefully there’d be no more trenches between him and his hopeful destination. While he hadn’t needed to leave the continental shelf at any point, the few dark trenches he’d traversed between elevations spooked him. He swam over those keeping near the surface during high noon.
He’d never seen those that rose from the deep at sunset from the midnight ocean regions. He had no desire to. He’d been warned by older, traveling apex mers that things from there sang a different song from the shallows folk, and cared far more about calories to consume than conversation.
The slants of light slicing through the water before disintegrating into shadow straightened, telling Katsuki the sun was high above. The floor bed now elevated toward what he hoped was a reef or even kelp garden, maybe even an island, a bar, or perhaps the start of a barrier structure. Dark stone peeked through the sand, the incline becoming steeper. Brighter algae and starfish appeared. He eyed what he passed, stomach clenching with hunger.
He hadn’t eaten since yesterday morning, yet still felt too heavy in the abdomen as he followed the incline. Like the hunger had decided to become a physical presence low in his gut to weigh him down. At home, shore reefs and tide pools offered all sorts of sustenance, and he possessed keen hunting skills. The emptier sand floors and rocky beds offered far less. His satchel already sagged, empty of anymore rations. It had been a hard decision between turning for the shore for shellfish or exploring the current’s change for a possible new reef. He’d taken the chance and was relieved at the promising signs.
Ahead, the underground mountains loomed out of the blue. He forced himself to not increase his pace, still needing to conserve his energy.
The sea floor split before him, part of it fanning off to a delta, flowing down while the rest steeply climbed into a past volcano’s bones. He ascended, eyeing the increasingly sharp drop to his left. It looked to be the head of another trench, a vein that shadowed into inky blue as it incrementally widened. The details were lost to him in the distance, the shelf fading into foggy shapes and darkness as the water deepened. Eventually it would drop into the abyss that all sea bottoms fell to. He hoped such a descent remained miles away.
As a shallows merman, his interest laid far closer to the surface. He changed trajectory until the deeper waters were lost to brightening slopes and clefts, the dark rock painted with colorful anemones and coral, starfish and other livelier denizens that swam or crawled about. Hopes lifting with the lightening water pressure, he couldn’t help but increase his pace. The light shafts now cut into the water at a sharp angle, and he looked forward to a night where he wouldn’t need to flush sand out of the small gills behind his ears and larger ones on his ribs.
The closer he came to the surface, the more excited. This was likely an atoll, a large one, and from what he could feel from the gentle currents, possibly the start of a chain of more atolls, bars, and islands, a haven of land close to the sun rich with life.
The only possible thing that might go poorly now would be the presence of someone who already claimed the territory and had no interest in sharing.
Currently, Katsuki had no interest in sharing either.
But first, he needed food.
He flicked his tail sharply to ascend, climbing up to peek above the water, bobbing with the waves to take in the palms, shrubs, and hear the air-thinned cries of gulls and terns. Satisfied at the lack of any human dwellings, he descending into the increasing waves, where all life swayed continuously with the ebb and flow of water rising and falling. He sidled up to a short cliff crowded with shells and happily yanked them free to use his strong claws and a rock to get to the satisfying meat inside, letting the tide rock him back and forth, a comforting motion he hadn’t realized he missed during his trek.
He’d only eaten three mollusks when he heard a clear vocalization, the triple points of his ears lifting in high alert. His eyes narrowed.
Of course. There was some other mer occupying this haven.
Katsuki flattened his bright, venomous fins once more, using his clawed hands to crawl along the ledges between bright coral, grass, and volcanic formations, seeking a suitable gap to traverse. Small fish flittered away, antenna from crevices and holes jerking back into hiding as he passed, even a small octopus jetting away.
The atoll surrounded a long lagoon, the end of it lost to his sight. The water lay wide and deep, a pleasing azure. The protected beaches within glittered with white sand and smooth rock formations. Katsuki wanted it, already imagining lounging in the sun on sand or stone, finding or digging himself out a nice den within. He wanted somewhere safe, somewhere he could protect, needed it with an insistent instinct buzzing at his brain.
Katsuki found where the bridge of land was narrow, creating a ditch in the rock between the outside sea and its noisy waves and the quieter water within. He clambered over the slippery stone cautiously, pushed by the waves each time, until he slid with them into the gentler waters beyond to start his search.
The other mer was not hard to find.
He was big, bright, and beautiful, and Katsuki immediately wanted to fight him.
Merfolk came in a few different categories, and it was always the spin of the tides that decided what a mer would be blessed as when born, parentage having nothing to do with such things. Katsuki was born the kind that generally kept near the shorelines. Shallows folk, and they tended to be the most common kind, fairly close to human size in the torso, though greater in tail. Then there was the next size up, rarer and often less predictable. Apex. Which Katsuki could argue against the name, because not only did he know there were things that could kill and eat them, but he hadn’t met an apex mer he couldn’t beat the fins ragged on. He made a point of fighting any that came near his pod that weren’t on established good terms already, because while some were friendly, some just plain weren’t.
He didn’t want to think of the abyss or leviathan merfolk. Far rarer and far less likely he’d ever run into one.
Before him, laying relaxed against an algae covered stone with half his body jutting out of the water to gossip with the damned birds, was an apex. The tail swayed lazily in the water, fins solid, and patterns in red stripes and spots. A tail bracelet, made of fishline with small onyx and pearl beads, circled the thinnest part of the tail. He could see the claws on dark red webbed hands, sinewy and strong, curled lightly around the edge of the stone, a bracelet of rope and shell on one wrist. Scars criss-crossed the body, an attractive array to the deep furrows of defined muscle.
The taller top tail fin and pattern told Katsuki this mer had been blessed with tiger shark features. The red mer was at least a third longer than him and over twice his mass, arms and tail that much thicker than his.
And he was in the territory Katsuki had already decided he wanted to claim.
Katsuki unlooped the satchel from his torso without taking his eyes off the larger mer. He set the strap around a jut of coral while his instincts blared at him. Impatience and urgency built. Blood already hot to act, he charged.
There were several ways Katsuki didn’t take after his sea blessing. Lionfish were slow swimmers, not needing to rely much on speed to hunt or fend off predators. Katsuki still possessed the muscular, long tail of all his kind, and he’d honed himself into a mean fighter. When he rammed into the apex mer and wrapped his claws around his tail, he rammed, pulling the other completely off the rock and swinging their back hard into the water with a slap!
The hight-pitched yelp might have amused him on any other day. Now his skin was too tight, Katsuki hot and irritated. He was hungry, heavy, and he wanted to break things.
The shark-blessed groaned, then gave a cut off grunt as Katsuki twisted and bashed him as fast as the water drag allowed into the very rock he’d been sunbathing on before. The tail in Katsuki’s grip slapped side to side, attempting to shake him off. The scales, rough and gritty, slid under his claws,, but he kept his hold, seeking to slam the bigger mer again.
This time the apex grabbed the rock, fingers gouging in. Algae and a few anemone’s swirled free into the disturbed water, but the grip kept him from being pulled. His tail whipped down, pulling himself upright. Katsuki released him, darting back to avoid a swipe of a clawed hand.
Strong! That pleased him. It shouldn’t, since it just meant he had a tougher fight on his hands, yet when the sharkly mer, mouth partly open still in shock, stared at him, Katsuki could feel the feral grin stretching around his sharp teeth.
Handsome was his next thought. The Apex had an impressive mane of red hair about a rather unassuming face and a mouth packed full of triangular teeth. His brows were small under a smooth forehead, his jaw slightly rounded and nose an adorable upturn. His irises were the same ruby as Katsuki’s, wide still with surprise. He wore a thick, hempen necklace, more shell and glass beaded into the net of rope resting just above his collar bone. The sunlight glinted from the shining abalone shell in the center.
“What?” the mer asked, obviously still confused by the attack.
Katsuki’s feral grin turned into a threatening snarl. “Get the fuck out!” he ordered, charging again.
Now that the apex saw it coming, he twisted to one side, the two swiping claws at each other briefly. He missed Katsuki, the smaller mer spinning deftly under the larger arm. His own claws only grazed near the other’s elbow when the larger mer shifted away with a jerk of his sturdy pectoral fin. Too light to cut.
Now those small brows bent with some offense. “Excuse me?”
Katsuki’s spines flared, the bright red and orange circular patterns flashing. Back arced, the spines stood tall as his faintly translucent fins spread wide, making him look much larger. The flash of size and color made the apex jerk back in alarm, and Katsuki was on him the next instant, snapping his teeth and lashing at him with claw and tail.
The strikes were fast and swift, propelled by flicks of tail and fin. Sand stirred and spun around them. Katsuki could hit hard. One knock from the apex in Katsuki’s ribs just below his gills showed he could hit harder. He focused on his smaller size and agility to dodge anymore strikes, ribs bruised as he sought vulnerable targets.
Several things occur to him as they struggled, the red mer more defensive but lashing out when opportunity presented itself. One, the apex knew how to fight, and while that thrilled Katsuki, it’s also raised alarm that he was not gaining any water. Second, the shark scales on the tail were not easy to penetrate. Katsuki’s small claws did no damage there, and the other kept a good guard on his torso and refused to let him at his back.
Thirdly, he was tiring out. Fast. Way faster than he should. Had going hungry really weakened him this much? Of course it must be a factor, but Katsuki had thought adrenaline would pull him through the scrap, having always been able to make even apexes turn tail quickly enough. But then, he’s never fought another mer in their own territory. The tiger shark-blessed had a lot more incentive than Katsuki’s usual rivals to stand his ground and win to keep his home.
Such challenges were not without risk. Merfolk frowned on murder, but killing during a territorial contest could happen. Apexes were also rumored to not only kill in such spats when they could, but indulge in cannibalism. Katsuki didn’t want to find out if that rumor held truth.
The last thing in his awareness, he did his best to ignore. His body reacted to the fight strangely. This was not a situation he should be aroused in, yet for some fucking reason, his dumb body was getting aroused, pressure building in his pelvis as his hidden cock swelled, making the heaviness there all the more distracting.
“Hey!” the apex chastised, backhanding out to brush Katsuki’s next attack away. “Listen, I think you need to take a swish back and think this through for a moment!”
Why the abyss did he barely sound out of breath? The water felt thick in Katsuki’s gills, his mouth and ribs pulling and fanning hard. It enraged him, made him feel mocked that the other remained unscratched and brimming with easy strength.
Katsuki screamed, darting back in to fight.
This time the apex caught him, going with the force of his attack to roll and grab his forearm. The two swirled close before Katsuki’s back bumped into the sandy slope of the lagoon’s edge, a puff of grit surrounding him.
Stunned, Katsuki stared at the apex hovering over him, his skin and scales awash with heat, breaths so hard they hurt. Those clawed, red and white hands enveloped half of his forearms, encircling them entirely. He wasn’t sure why that stupefied him so much.
Brow pinched, the apex breathed out roughly, then inhaled to speak. The stern look on the shark-gifted left abruptly, whatever he’d been about to say gone. He leaned closer, nostrils flaring and pupils spreading. Katsuki flinched back, baring his teeth. “Oh, you’re…!”
Katsuki liked to win fights with just his prowess when he could. Something in his brain panicked. His feathery pectorals flared, and while they did not contain any of his venomous spines, the smaller pelvic fins did. He twisted, seeing the red mer’s eyes widen as he stabbed at his side with the spine on the outside of his hip.
It didn’t pierce. The tip of it scraped and stood against the muscled torso, which now had the same rough texture as the damn armored tail.
“Sorry, little guy,” the apex said, sharp teeth on display in a grin. “Those spines your sea blessing gives you probably pack a punch, but you gotta get through my gift first.”
He trembled, face twitching into increasingly menacing scowls before he cried out in blind rage and fought. Sand and sea grass whipped up into a blinding slurry as the two rolled and wrestled along the lagoon floor.
By time the sand settled, Katsuki struggled to breathe, wrists still in a tight hold, tail swishing back and forth weakly as the other kept them balanced on the bottom. The water above now glittered with orange and gold, the sun well on its way to setting.
“Easy now. Just relax. We don’t have to fight, you know.”
Katsuki bared his teeth, poisonous spines flaring uselessly. The larger mer’s grip remained strong as an anchor chain, leaving Katsuki to open and close his finned hands uselessly against water. He flipped and swiped his tail along the striped scales, but just as before, his barbs couldn’t penetrate.
“You’re a feisty one,” the red-scaled mer said, and it pissed Katsuki off even more that he sounded delighted. The voice lowered as he leaned in. “Pretty, too.”
Katsuki froze for all but a second before he exploded like an ocean floor vent. “FUCK YOU! I AM NOT PRETTY!”
His renewed struggle took the larger mer by surprise, sending them flipping in frantic jerks of fin and muscle. He didn’t let go, even when Katsuki got a brief bite on his arm that finally sank past the less armored torso skin, drawing blood. The red mer made a sound at that, like an inhaled snarl, jaw wide and sharp teeth snapping back in retaliation inches from his face. Katsuki reeled back frantically, trying to separate them again. The claws dug into his forearms, and Katsuki had to bite back a yip as they punctured and made his webbed fingers go stiff.
Right, he did not have this tiger shark by the tail.
Water burning through his gills, chest heaving, he hung in the larger mer’s grip, fins sagging as he attempted to simply breathe.
“You done?”
He didn’t respond, dread numbed with exhaustion. He’d lost. They both knew he’d lost. A smarter mer would have swam away when the contest proved too risky and hopeless. Katsuki hadn’t been able to, driven to win.
“All right. You’re coming with me.” The powerful tail flicked and swayed. Katsuki was dragged along by his wrists. The shark mer drove them past the lagoon’s reefs through a narrow chasm, then down into deeper water, the eastern side of the atoll already dark in shadow. And Katsuki couldn’t stop him.
He truly might learn first hand if those cannibalism rumors were true.
He gulped water, gills fanning with exertion still. A tremble grew in his muscles as he tried to muster up more strength to throw the mer off. He failed. They continued to sink down the steep side of the atoll. The water pressure increased with the additional meters. Normally Katsuki would barely notice it, but now with his muscles trembling and burning, it weighed on him. At least they were not descending too deeply, sea plants still plentiful along the dark volcanic rock when the shark-blessed turned to bump on a generous shoulder of stone and sand. A striped school of fish zipped away from them. A passing sea turtle halted, slapped its fin to turn and hurried away.
No help there.
Katsuki wanted to lay in the sand and catch his breath. His fins fanned weakly in time with his panting, the water feeling too thick to inhale properly, his muscles hot and bruised. Only The shark mer’s longer tail kept them balanced upright on the atoll’s shoulder. Those intriguing red eyes casted around behind Katsuki at the cliff wall before he refocused on Katsuki with a big, sharp grin.
“You know,” the mer said conversationally, and dammit, it infuriated Katsuki that he sounded so chipper. “I didn’t want to fight you. If you’d have asked nicely, I would have let you hunt in our territory.”
Katsuki could only pant, brow bent up in confusion. “Our…?”
He was so exhausted, he only felt the presence looming up to his back an instant before a chest pressed against him, forcing his spines down before they had a chance to lift defensively. Long fingers slid under his gills, capturing his middle. He could barely see pale skin and purple in his periphery. He froze, blood dropping to arctic temperatures at the deep surety of the quiet voice in his ear.
“That’s right, little fry. Our territory.”