Chapter Text
The six weeks that it took for Kirishima to order and receive a new surfboard were the longest and unhappiest that he could remember living through for a long time. He went to the beach with his friends the same way that they always had, but was forced to sit on the sand and watch as they enjoyed beautiful waves and glittering perfect water without him.
Some days he swam, following the group out as far as was safe and coasting in the shallows for a while, but it didn’t have the same satisfaction as being on the board, riding that line between excitement and terror, never quite knowing which way a wave was going to take you once you were on it. But finally the new board arrived and he ran into the surf with a laugh, relishing the feeling of the water below him, the smooth glide when he was finally able to stand and ride a small wave.
When the water calmed and the sun came out in earnest he remained in the water, laying on his board with his feet dangling in the ocean, finally at peace now that he was back where he belonged.
He was almost dozing when something cold and clammy brushed against the hand that was trailing in the water, surprising him to such a degree that he lept up, falling off of the board and splashing hard into the water on the other side of it. He was about to push back up when he saw a familiar shock of purple in the water in front of him, a pair of wide eyes gazing back.
“Hi,” he said, so excited to see his friend that he forgot that he was underwater for a moment, the word coming out almost entirely as bubbles.
He returned to the surface to breathe, waving to his friends and giving them a thumbs up to let them know that he was okay before ducking down again.
It was on that second dive that he noticed how different Shinsou looked from the last time he’d seen him. Gone was the generally placid demeanour, the calm collected creature he’d met was gone and in his place was a flushed panting man who seemed to be struggling to keep himself level in the water.
“Shinsou?”
“Need,” Shinsou managed, surging forwards and pressing his hands to Kirishima’s chest, running a long slightly barbed tongue up his neck in a manner that had Kirishima paying far more attention in a matter of seconds. “Spring. Please-”
The words huffed in his ear were breathy, desperate and needy in a way that Kirishima didn’t think anyone had ever been with him before. Was Shinsou really suggesting what he thought he was? Regardless Kirishima was immediately rock hard, straining against his board shorts and blushing from neck to navel. He hauled himself up to the surface, gulping a breath and holding himself aloft on his board, doing his best to look as though he was just leaning there to enjoy the view even as deft webbed fingers began tugging at him, pulling his shorts down and out of the way without any ceremony at all.
“We’re going to head for a drink, you coming Ei?” Sero bellowed at him from the distance, but Kirishima shook his head.
“No, I think I’m just going to stay out here and get used to the board a bit more. I’ll join you later man.”
“Whatever, don’t stay out too late.”
He gave another, slightly shaky thumbs up, before dipping back below the water. Because while he wasn’t quite sure what was happening, he sure as hell knew that he wanted to stay and find out.
***
Shinsou was hot . When the mating season rolled around the way that it always did in the spring he’d expected to follow the routine that had worked for him every year since he grew to adulthood. He would eat well, rest as often as he could, and remain in his cave as much as possible until the entire ordeal passed him by. He had no mate – nor any desire for one – and he had always been perfectly happy to pleasure himself when the need became more than he could ignore over those few spring months.
But when the season began the ache in his chest was overwhelming. No relief was sufficient to cool the burning in his core, no food able to satisfy his ever present hunger. When he closed his eyes all he could see was a wide sharp smile and a shock of bright crimson hair, his body calling for a mate that he didn’t have.
The human man had ruined him in their one small meeting. He craved the wide hot hands that had held him so easily, the skin that warmed without the need to bask and bathe in the sun. He was plagued by a desire to touch and feel and taste a man that he barely even knew. Over time the need overtook everything else. He couldn’t eat, couldn’t sleep, there was only the aching for a mate. A mate who didn’t even know the hold he had on the merman.
So – when finally it was more than he could bear – he went out in the waters in search of the one being who would be able to soothe him.
***
If he’d been asked even a week before Kirishima would have said that there was absolutely no way that he would ever have sex in public. That it just wasn’t right to risk being seen doing something that should be a private matter. It wasn’t manly to force people to see things they didn’t want to, either.
But when Shinsou pulled off his shorts and swallowed down his cock in one long incredible stroke it was all he could do to hold on to his board and stifle his moan. The mouth around him was cool and wet, the tongue stroking against him just the right amount of rough to make his breath catch in his throat. Shinsou’s hands were around his hips and he seemed intent on swallowing him whole, letting Kirishima’s cock hit the back of his throat over and over at a pace that was almost too fast.
With a moan that he had to stifle by biting against his forearm Kirishima reached down to tangle his fingers into Shinsou’s hair, taking a firm grip and rocking his hips, keeping pace with the eager man below the water, letting his eyes roll back into his head – despite his fears of being seen – and losing himself in the feeling.
It was easily the best mouth he’d ever had around his cock, the tight sucking combined with the laving of Shinsou’s lightly barbed tongue quickly bringing him to the edge of pleasure, his legs trembling in the water and light breathy moans slipping from his lips. He was sure that anyone who passed on the beach would know exactly what was transpiring below the waves, that he would be caught and punished for such unmanly behaviour. But it felt so good, so dirty in all of the best ways that he didn’t think that he’d have been able to pull away even if he’d wanted to.
“Ah Shinsou -” Kirishima gasped, slipping below the water when one hand slipped around his balls and tugged. He crashed their mouths together, sliding his tongue between plump lips and groaning at the feel of the lithe strong body that was now flush with his. There was a stirring between his legs and he broke away from Shinsou just long enough to look down and see a thick tentacle winding around him, protruding from above a short slick slit in the top of Shinsou’s tail. The tentacle slid and pumped, tugging him in a delicious rhythm while Shinsou pressed his lips to Kirishima’s chest and neck and shoulder, anywhere that he could find to kiss and lick and bite .
“Shinsou I- I!”
There was no time for any other warning, the surge of pleasure overtaking Kirishima hard and fast, his body spasming and his cock pulsing as streams of thick hot cum made a mess of Shinsou’s stomach and tail.
Kirishima surfaced with a gasp, panting and clinging to his board, Shinsou rose with him, his hands still pressed against his skin, a long sigh coming from him when he laid his head against Kirishima’s back.
“Come with me to the island,” Shinsou whispered. “Please, I need you.”
Kirishima untangled his discarded shorts from around his ankles and tugged them back up and around his waist, pulling himself up onto his board to be guided towards the small island that he had visited only once before. Shinsou swam quickly ahead, setting a place that was difficult to follow, but Kirishima paddled hard, making huge strokes with his arms and kicking his feet so violently that it almost looked as though there was an engine in the water behind him, determined not to miss the opportunity hat was being presented to him.
Shinsou led them around to a small sandy cove, turning the moment that they were out of sight of the mainland and grabbing Kirishima around the neck, pulling him back down into the water so that their lips could press together again. It was almost natural for Kirishima to pull the merman up into his arms, to find his feet and carry him up out of the water. He was as gentle as possible when he laid Shinsou out on the sand, looking down at the merman who was again flushed and panting, his eyes full of a desire that made Kirishima’s heart flutter.
“Tell me how to help you, Shinsou,” he whispered, kissing down his neck, sucking small marks into his shoulder and relishing the lustful sounds that fell from him with every touch. “Tell me how to make you feel good.”
With a huff Shinsou grabbed one of his hands, tugging it down and pressing it against his waiting slit, bucking up into the touch and whining in a way that made his desire all too clear. Kirishima kissed and sucked his way down Shinsou’s chest until he was level with the slit, and the writhing tentacle that protruded from the top of it. He hesitated a moment, looking up for permission before licking a long stripe teasing over the softened scales.
Shinsou keened, a hand fisting into Kirishima’s hair to hold him there, and that was all the encouragement he needed. He lapped and sucked, pulling the tentacle into his mouth and tangling his tongue with it in a passionate kind of kiss that made Shinsou buck and whimper. He was certain that the man splayed out on the sand beneath him was the most beautiful that he had ever seen, his hair mussed up and spread around his face, a flush in his skin, soft plush lips, his gills fluttering and tensing with every touch. .
When Kirishima finally popped off of Shinsou’s tentacle dick he felt himself tugged upwards, pulled into a fervent kiss that made his head spin and had the blood rushing right back towards his cock despite his recent release.
“Inside,” Shinsou panted. “Inside please.”
Hands guided Kirishima into place, lining up his dick with Shinsou’s waiting slit, the tentacle wrapping around him and tugging as though to encourage him to move faster.
“You’re sure?” Kirishima asked, his breath catching in his throat. “You want-”
“It’s all I want,” Shinsou nodded. “Please, please don’t stop now.”
With their foreheads pressed together, breaths mingling between them Kirishima sank slowly into the wet heat, squeezing his eyes closed and doing his best not to cum right there and then like a teenager when he felt Shinsou’s body open to accept him. It was so tight, sucking him in and squeezing, the tentacle sliding around to tug on his balls and tease his ass. That alone would have been enough to send him over the edge, but Shinsou was making such pretty sounds on top of it all that Kirishima was struggling to hold himself together.
He took a second to breathe, taking a second to let the intense pressure in his core recede a little, and then he started to move. Slowly at first, long hard thrusts that made Shinsou arch and gasp, his hands clawing at Kirishima’s back and shoulders, clinging to him like he was a lifeline. That only made Kirishima want to move harder, something desperate and primal taking him over as he started to pound into Shinsou in earnest, bracing one hand behind Shinsou’s head to allow him to move faster and harder.
“Ah, ah fuck! Kirishima!”
Shinsou whimpered and moaned with every movement that Kirishima made, throwing his head back and digging his fingers into the sand. Finally Kirishima reached between them, tugging his tentacle up and thumbing over it with every thrust, and that was enough to give Shinsou the release he so desperately needed. His eyes glazed and his fins trembled, slit sucking against Kirishima even harder, dragging him deep and holding him there.
When he looked down and saw Shinsou falling over the edge of bliss Kirishima lost any control he had over his own pleasure, spilling inside of Shinsou with a startled grunt, falling forwards to pull his partner into a lazy kiss before flopping down panting beside him onto the sand.
“Whoa,” he breathed, swallowing hard and trying to steady his breathing. “That was. Whoa .”
“Yeah,” Shinsou hummed, reaching across to rest a hand on Kirishima’s chest. “Thank you.”
“No need to thank me,” Kirishima chuckled, rolling onto his side with a soft smile, pulling Shinsou to face him and brushing their noses together. “Though I’ll admit I was a bit surprised when you appeared, I can’t say that it was a bad thing.”
Shinsou flushed, suddenly bashful despite being taken apart by his human partner only moments before.
“Sorry about that. It’s uh… it’s mating season and apparently my body really knew what it wanted this year.”
“Mating…season?”
“Spring every year. Our instinct drives us to take a mate and…” he flushed again, not able to meet Kirishima’s eyes. “Our kind tend to mate for life but I understand that that’s impossible to ask of you. I just appreciate your help. I don’t know what would have happened if you hadn’t been in the water. Or if you didn’t want me.”
Kirishima wrapped his arm around Shinsou’s waist, tugging him close and nestling his head into Shinsou’s shoulder.
“I don’t know that I can promise mating for life, that’s a big decision to make right now. But…this was pretty amazing. You’re pretty amazing, so. If you need my help again…”
Shinsou had to laugh, they were both suddenly so awkward when minutes earlier they had been fucking like animals. It was endearing, and somehow it made the whole situation easier on him.
“The season lasts another few weeks at least. So, if you wanted.”
“I’ll come back every day to help you through it, if that’s what you need,” Kirishima said, smiling a little. “I can bring a tent, enough food to keep me going and just stay with you. I’m due a holiday and…” he blushed, not quite able to hold Shinsou’s gaze. “And if every time it’s going to be this good.”
“Really?”
“Really. You’re interesting and attractive and that thing you do with your tongue? I can’t see why I wouldn't want to see you again.”
“Thank you, Kirishima.”
“Eijirou, to you. You’ve had your mouth on my dick I think we’re past formal names.”
That made Shinsou laugh, and he cuddled up on Kirishima’s chest in earnest, letting himself be pulled over into strong arms when Kirishima flopped onto his back with a laugh.
They stayed on the beach together until the sun started to dip towards the horizon, and Kirishima knew that his friends would begin to worry if he didn’t return. But he promised to swim out to the island in the morning, with everything that he needed to remain there for a few weeks if that’s what Shinsou wanted.
Because whilst he didn’t think he could faithfully promise Shinsou forever, human or not, at least for the short term he couldn't think of anyone else that he would rather be with.