Thread by @erisabesu3

Thread fic for #atsuhina #侑日日和 event, Day 2: Fantasy AU ✨🧜‍♂️ (#nsfw, semi-public sex, mer!people)

Miya Atsumu /loves/ the water.

Hinata hasn't been dating Atsumu that long, but he already knows this truth - Atsumu is at home in the water in a way he's never seen before.

It's wasteful, actually, how long Atsumu takes in the locker room showers, humming and grooming himself unhurriedly under the warm spray

while the rest of MSBY typically gets in and gets out without any fuss.

Atsumu's locker has shampoo and conditioner, two kinds of bodywash, a loofah, sponge, and washcloth, and a moisturizing body oil he finishes with while wet from head to toe. Once patted dry with his towel,

he has a special lotion that smells like jasmine and salt that he takes his time rubbing into his skin, especially his elbows and heels.

The other guys taunt him regularly for his prissy care routine, even Sakusa - whose routine is equally thorough but not quite as over the top.

Hinata finds the whole production fascinating, and doesn't mind hanging back while Atsumu pampers himself, because now that they're /boyfriends/ - a thrilling word that still makes Hinata "doki-doki" when he has the chance to say it aloud - he gets to watch, and sometimes help.

He's still a little concerned about the amount of water Atsumu uses each day after practice, or at his apt, where they frequently return after their dates.

Atsumu often suggests bathing together, and shows Hinata the same level of care when they're intimate, whether it's soaping

his hair or washing every last inch of him, or cuddling him in the tub, fingers tracing lazy lines across his skin and kisses pressed to his wet neck.

They have a lot of sex from day one, and it's good, they're athletes with a healthy appetite and Atsumu finds him as attractive

as Hinata finds Atsumu. (He's always been attracted to Atsumu, to be honest, and it's still kinda like a dream that he gets to have him like this, mutual affection and devotion.)

Hinata's had some past experience with shower sex, and bathtub sex and (ahem) fooling around in the

locker room, including the shower stalls. But he learns pretty early on how fooling around when there's water involved gets Atsumu worked up the most.

Even going to the local pool with their teammates can be a problem - the slightest suggestion of something racy while they're

goofing around gets Atsumu in the mood in record time. Hinata has to be careful or Atsumu will corner him against the side of the pool, and tease him with kisses while grinding their hips together underwater until they're both aching for it.

And sometimes Hinata doesn't want to be careful and pulls down their bathing suits enough to jerk them both off before anyone notices, unable to resist the thrill.

They scurry out of the water afterwards and leave without any explanation, dashing home to wash off the chlorine--

and immediately start round two. <3

(Hinata does feel a bit guilty about ejaculating in the pool, and resolves never to do it again, but. 😩 Atsumu makes him weak! 🥺)

So all things considered, when Meian arranges for a team excursion to the beach, Hinata is /very/ surprised when Atsumu chooses to mind their things by the umbrella chairs instead of taking a dip in the waves like the rest of them.

"Atsumu-san, let's go swim! Aren't you coming?" Hinata beckons, holding a beach ball.

"Nah, go on ahead," Atsumu waves him off. "Don't wanna get too much sun."

He picks up Hinata's straw hat and puts it on, flashing a cheeky grin and plopping down in a beach chair.

Sakusa, also sitting in a beach chair with a book, looks down over his sunglasses. "I can watch the team's belongings, Miya. You can go ahead with Hinata."

"Thanks Omi-san! Let's go, I'll race you to the water!" Hinata grins and hops a few steps towards the ocean, expecting

Atsumu to give chase - but he doesn't move.

"Sorry, Shouyou-kun, I'll swim later," Atsumu shakes his head, crossing his legs. "You go have fun!"

"But you love the water!" Shouyou frowns, balancing the beach ball on his hip.

Atsumu's eyes dart to the side. He bites his lip.

Then he takes off the straw hat and starts fanning his bare chest, sighing with exhaustion. "Dontcha remember how many beach volley games we all just played? Need some time to catch my breath!"

"You played in 2 games, Miya," Sakusa deadpans. "That's hardly enough to sit you on

the sidelines like this."

Hinata lifts his brows as Atsumu flinches - Sakusa's right. The only ones who played more than two games were Bokuto and himself, and Bokuto played 3 games to his 5, and was still out there having fun in the sea.

Right on cue, Hinata hears Bokuto's

voice calling his name from across the beach and asking for the ball. Hinata turns around to see him jogging over to them. He waves his arm in the air, then makes an OK sign and turns back to Atsumu.

"You're really not going to come play?" he asks, still puzzled.

Atsumu gives an awkward shrug, struggling to come up with another excuse, and Sakusa tsks.

"I don't know what's going on with you, but you're making your boyfriend sad. And that's /really/ sad, Miya." Sakusa crosses his legs and reopens his book, clearly ignoring them.

"Oh come on!" Atsumu rounds on Sakusa in protest.

Hinata's quick to wave a hand. "I'm okay Atsumu-san! You don't have to come, it's fine if you want to stay here."

Atsumu turns back to him with a pained expression, and Hinata feels a pang. But they're interrupted by Meian and

Tomas arriving with bags of ice for the coolers.

"Miya, can ya help get the lids?" Meian asks.

Atsumu leaps up and opens the coolers so Meian and Tomas can pour the ice over the team's stash of water and pocari, and the big bottle of aloe gel in case of sunburns.

"Hinataaaaaaaa!!" Bokuto bounds up to the group and hip-checks Hinata.

"Whoa!" Hinata yelps, righting himself but losing his hold on the colorful beach ball, which Bokuto snatches from the air.

"Ha-haha!" Bokuto exclaims triumphantly, twirling the ball. "What's the hold up?"

"Hold up?" Meian tilts his head, stripping off his shirt and shoes.

"Miya refuses to swim with Hinata," Sakusa interjects.

"Wha!" Hinata starts to protest, and Atsumu squawks, giving Sakusa a murderous glare.

"That's not cool, Tsum-Tsum!" Bokuto shakes his head, but Atsumu's

too busy kicking sand onto Sakusa's feet to see.

"You swim all the time, what's the problem?" Tomas asks, also shedding his shirt and flip-flops from their errand to get the ice.

"He doesn't have to!" Hinata holds up his hands. "He can stay here if he wants."

The others scoff.

"Since when is Miya ever the last one in the water?" Meian puts hands on his hips.

"Since when is Miya hiding in the shade when he could be the center of attention?" Tomas smirks.

"Since when does he pass up a chance to makeout with my disciple?!" Bokuto adds.

Sakusa closes his book, and flashes a pointed look overtop his sunglasses. "Since when does Miya think he can get away with throwing the lot of us into the pool at one time or another, and expect not to suffer the same fate?"

Everyone turns to Atsumu, who starts to back up.

"You're so right, Omi-Omi!" Bokuto nods, grinning and closing in.

"Now hold on!" Atsumu wards them off with arms extended.

"Points have been made," Meian chuckles.

"Um—!" Hinata shifts on the sand, a little unsure which side he should be on.

"What's wrong? We all know you

can swim like a dolphin," Tomas adds, cracking his knuckles.

"Uh, guys, can ya calm down please?" Atsumu keeps backing up until he hits the railing of the wooden walkway up to the pier.

"Last time at the pool ya ruined my fitbit," Meian comments. "So no. Yer goin' in."

"Wait!" Atsumu pleads.

Before Hinata can do anything, Bokuto and Meian hoist Atsumu off the sand and carry him by the shoulders and ankles towards the shore.

Hinata and Tomas jog alongside, laughing the whole way, and Hinata can't deny it's pretty funny to witness, especially

with Atsumu wiggling and wailing that, "Ya don't wanna do this! Put me down! Noooooooo~!"

Hinata's inner gremlin finds all of this very, very amusing, because they're right—Atsumu has thrown all of them in the pool at least once, and so he sorta deserves a taste of his own

medicine.

When the four of them reach the very edge of the water and splash further in, Atsumu becomes frantic. Together, Meian and Bokuto wade in up to their calves, and start swinging Atsumu back and forth.

"Shouyou-kun!!!" Atsumu screeches, while Meian counts, 1, 2, 3—

They let go and toss Atsumu towards the rolling waves in a high arc. He sails over the water, limbs flailing, and then crashes through the surface, hands and feet the last they see of him as he sinks below the water and disappears from their sight.

"Whooo!" Tomas cheers, echoed by Bokuto and Meian who give each other high fives and whoop.

Hinata laughs with them, wading in further and looking for Atsumu's blond head to pop up at any moment. They gather in a line and laugh, watching the place where Atsumu landed.

Hinata brought the beach ball along and he squeezes it between his hands, scanning for Atsumu's head, and trying to anticipate where he'll come up for air.

Tomas shields his eyes with his hand, squinting across the water.

"Where'd Tsum-Tsum go?" Bokuto asks, also squinting.

Hinata frowns, moving further into the waves, trying to catch any sign of him.

"Prob'ly settin' us up for a prank," Meian answers, but he's also frowning and this sends a chill through Hinata's whole being.

"You don't think he hit his head or anything, right?" Hinata asks, pulse spiking at the first signs of worry. "He's not hurt or anything, right?"

"Nothing to hit his head on out there," Bokuto shakes his head.

"He's a good swimmer, Hinata," Tomas assures him.

"Wouldn't have

thrown him in if it was dangerous," Meian adds, squeezing Hinata's shoulder. "But the current may have pulled him further down the beach. He's gotta be close, ok?"

Hinata nods, but he can't shake the feeling that something is wrong. The way Atsumu called his name right before

he hit the water sounded so /desperate./

Another two minutes pass and when there's no sign of Atsumu, Hinata feels chills again, and a lump forms in his throat.

"I'm going after him!" Hinata declares, shoving the beach ball into Bokuto's hands.

"Hinata, wait!" Meian reaches

for him but Hinata's already plunging waist-deep into the waves and diving into the sea.

He swims swiftly away from the beach, and when he comes up for air, he can hear his teammates calling out for him, but he ignores them.

Atsumu's still out there somewhere! He might be hurt or need help—Hinata swims like Atsumu's life depends on it, quashing the panic in his heart in favor of maintaining his swimming form and his breathing while the ocean waves work against him, pushing him back towards the shore.

Hinata swims out past the other beach-goers, pausing periodically to look for that familiar burnished gold of Atsumu's wet hair.

No sign of him.

He swims past the line of waves that attract surfers, careful not to get in their way, and looks all around for any sign of

the man he loves.

Nothing.

Hinata's lip quivers, and his eyes sting, but he blames the saltwater and dives down to peer through the murky haze and scan for any sight of Atsumu, any flash of leg or his turquoise bathing suit or swirl of blond hair...

Still nothing.

Hinata comes back up to the surface, gasping and swiping the wet from his eyes. He looks around again, and when he doesn't see anyone that looks like Atsumu he keeps swimming away from the beach.

Meian's right about the current—it sweeps along the seafloor at an angle

to the shore, but there are also currents that pull from the shallows into the deeps, and it's these undertows he's the most worried about.

What if Atsumu got stunned when he hit the water, and the undertow dragged him so far out from the shore he couldn't fight it?

Fear coils in the pit of Hinata's stomach, but he pushes on, swimming farther and farther out, then diving down and hoping to catch any small glimpse of Atsumu.

He /has/ to find him before it's too late!

Hinata searches underwater until his lungs are straining, and then returns

to the surface, gulping air. He's pretty far out from the beach and people, but he's determined to find Atsumu, and will not give up.

Hinata pulls his arms through the water, widening his search into deeper waters, when something suddenly brushes up against him and grabs hold—

Hinata's fear surges into his throat and he shrieks, batting the thing away and hoping it's not a shark, kicking his feet and flailing with all his strength—

"Shouyou-kun, Shouyou-kun!" Two arms wrap around Hinata, pinning his arms to his sides.

Hinata stops his thrashing, blinking the saltwater from his eyes and recognizing Atsumu's voice, his face, and the feel of Atsumu's chest pressed against his. But—something's weird?

"Shouyou-kun! The hell ya doin' swimmin' out this far—any further an' ya could've drowned!" Atsumu hugs him tight. "Scared me to death!"

With arms pinned Hinata can only bend his elbows and brush Atsumu's sides, so relieved his boyfriend's okay—and alive—that he yells at him.

"Atsumu-san I was worried sick! What happened to you? We waited for you to come up but you disappeared! /You/ scared /me/ to death! I've been looking for you everywhere!"

Atsumu kisses him passionately, and Hinata finds his anger melting away with the caress of tongues, and the

taste of the sea. Atsumu eases his hold enough for Hinata to wind arms around his neck, fingers curling into Atsumu's wet hair as their mouths work together, exchanging deep kisses and some tender pecks and nibbles. Hinata's so happy to be reunited he almost doesn't notice that

they're both strangely buoyant, his weight in the water held up by Atsumu's embrace alone. They bob and sway, kissing without caring for anything but each other, until Hinata's thumb brushes over a strange roughness on Atsumu's neck and he gasps, abruptly breaking off the kiss.

"Ah! C-careful, Shouyou-kun," Atsumu shivers, angling his head away.

"Sorry!" Hinata says instantly, clasping Atsumu's shoulders. "Did it hurt? Are you wounded?"

Atsumu meets his gaze, then shakes his head. "No... not exactly?"

Hinata frowns, and then his eyes catch movement.

Slowly, a series of... flaps? Flutter on each side of Atsumu's neck. Hinata leans closer to see, and Atsumu lets him, hands tense on his waist.

A moment later, the flaps move again, and Hinata's eyes go wide. These are /gills./ And... Atsumu seems to be breathing through them.

There's a rhythm to their delicate movements and Hinata looks up at Atsumu, eyes full of questions.

"So ya see, Shouyou-kun..." Atsumu chuckles, clearly nervous. "I kinda... have somethin' to tell ya... that I didn't get to tell ya about yet..."

Hinata nods, waiting for more.

"Um...." Atsumu winces. "Please don't freak out?"

Hinata tilts his head, curious... and then he feels something brush his leg under the water. He bites back the surprised /eep/ at the contact, and tries to hold still. It feels like he imagines a large sea animal might feel,

like a seal, or a dolphin swimming very close by.

Atsumu takes Hinata's hand and smoothes it down the front of his body, curving over his abs and along the side of his waist until Hinata can feel the slickness of wet skin turn into something else, something finely textured

on his hip. Hinata keeps moving his hand down, curious, and then full of wonder when the pieces click and he understands that he's touching Atsumu's /tail/, that he's a mermaid. A merman?

Atsumu lifts his tail up so Hinata can touch his fins, run his fingers across their edges.

Hinata admires the sleek blue-gray scales and scalloped details before the tail slips back down under the water and resumes the subtle motions that have been keeping them afloat.

Atsumu peers at him, so vulnerable though Hinata thinks he's trying to keep his face neutral.

He cards a hand through Hinata's wet hair and waits, and all Hinata can think is how special it is to be trusted this way, no matter how it came about. But also?

Hinata grins, then bursts out laughing. "Holy shit! Holy-freaking-shit!"

Atsumu's smile is hesitant, his cheeks flushing pink. "Yer takin' this pretty well, then?"

Hinata can't help sparkling, grabbing Atsumu's shoulders. "This is amazing! Cool! You're a fish person!"

Atsumu ducks his head, flushing brighter. "We prefer the term /Seafolk/ actually."

"Sure!" Hinata grins. "So you can breathe under water? How fast can you swim? Can you fight a shark? If you're a fish why do you eat fish? Can you talk to them? Wait 'Seafolk?'" Hinata gasps. "There's /more/ of you? How many? Where do you all live? Oh my god, how do you /pee/?"

"Shouyou-kun!" Atsumu gives Hinata a little shake, his face neon red. "I'll tell ya everythin' but we got a big problem right now an' I needja to focus!"

"Sorry, sorry!" Hinata takes a breath to calm his excitement. "So what's the problem?"

Atsumu's eyebrows shoot up, and he

gestures to his gills, and flicks his tail fins up beside them. "Hello? Can't exactly swim back like this, can I?"

"So just change back!" Hinata smiles.

Atsumu groans and bonks their foreheads together. "'s not that easy or I would'a done that already.

Can't change back when 'm in saltwater, keeps me in this form. Hafta dry off completely first, an' that's gonna be real difficult on a public beach—besides, they're probably lookin' for us and maybe even called the rescue squad by now, and that'll be /really/ bad for me!"

"Oh my god!" Hinata says, the full impact of the situation finally getting through to him.

Atsumu exhales. "So yeah, one thing at a time, ok? First is to let the Cap and everyone know we're okay, nobody drowned. I don't look all that different from the waist up, so I'll swim us

close enough to wave to them, so they c'n tell it's us."

Hinata nods. "Okay, got it."

"Hang onto my back, okay?" Atsumu turns smoothly in the water so Hinata can take hold of his broad shoulders. "An' go ahead and put yer knees on my waist, and squeeze tight.

Don't wantcha to fall off."

Hinata complies, bracing his knees on either side of Atsumu's narrow waist, and holding on tight. Atsumu cranes his neck to flash a calm smile, then he leans forward and propels them back towards the shore quite faster than Hinata was expecting.

He squints his eyes against the wind, and Atsumu guides them so effortlessly on a course that avoids any other people that he can't help but be impressed. They go far enough in to recognize the entire MSBY team in a clump on the sand with two lifeguards with red floating devices.

Hinata's stomach drops, remembering how scared he was when he thought Atsumu was drowning. Their teammates were probably just as scared, maybe more since Hinata hadn't come back either. To suddenly lose two teammates to the ocean would be terrifying!

Atsumu brings them to a stop, the water shallow enough that Hinata can feel how Atsumu's tail has to bend backward behind them to keep from hitting the sand below.

"They should be able to see us now. Wave yer arms." Atsumu puts his arms up and Hinata follows suit.

After a moment, their teammates start waving back to them, Inunaki jumping up and down. Even Sakusa is there waving and wearing Hinata's straw hat, looking disgusted.

"They see us!" Hinata exclaims. "Helloooooo Caaaaptaaaain!"

"Oyyyyyy!" Atsumu adds, holding two thumbs up.

"The lifeguards are going back!" Hinata says.

Atsumu nods, sighing. "Good. Okay Shouyou-kun, next part's up to ya." He twists so Hinata can slide off his back and tread water beside him.

"What do you mean?" Hinata asks.

"Can't go any closer like this, so ya gotta go back to shore and tell 'em I'm okay. Tell 'em I got swept out on a current and lost my bathing suit, an' ya gotta bring me another one."

Hinata glances down in the murky water at the mention of a bathing suit, but realizes that

means Atsumu's /naked/, and suddenly he feels the need to avert his gaze, cheeks burning.

"O-okay, sure," Hinata replies. "I'll get you another suit. But then what? I can bring it to you but you won't be albe to wear it, right?"

"No, but if they know we're okay, and ya get

a spare suit for later, then ya can also tell 'em we wanna spend time together, just us, and that we'll meet them back at the hotel tonight. Give us time to figure out the rest. Okay?"

"Oh yeah, good idea! Gets them off our backs for a while!" Hinata grins.

Atsumu smiles, and pulls Hinata in for a kiss. "Alright, go on then, and I'll wait for ya in the deeper waters 'till ya get back."

Hinata kisses him once more. "Be right back!"

Hinata swims back to shore, and endures the scolding and teasing and carrying on by their MSBY

Captain and teammates, who are only too amused by Atsumu having lost his swim trunks, but also very relieved that the both of them are none the worse for wear after the ordeal. Hinata accepts their hugs and slaps on the back good-naturedly, and endures their cat-calls

whistling when he explains that they're going to stay in the water and have some couple-time, but will be back later that evening.

Meian rolls his eyes like the tired babysitter he is, but Bokuto offers to take care of their things until they get back later on, and Hinata

thanks him with a huge hug. He grabs Atsumu's spare swimsuit and ties the drawstring to his wrist, waving at them all before heading back into the ocean and swimming out to where he left Atsumu.

Soon enough, Atsumu appears at his side, swooping Hinata back into his arms.

"Well? How'd it go?" Atsumu asks.

Hinata gives a thumbs-up, the spare swimming trunks attached to his wrist. "Bokuto-san's taking care of the rest of our stuff and we'll meet them later at the hotel!"

Atsumu sighs audibly in relief, giving Hinata a little twirl in the water.

"That's great news. Wasn't sure what I was gonna do when they threw me in! Panicked for a moment. Just swam away before anyone could see."

Hinata strokes his cheeks. "I'm so sorry about that. I should have stopped them."

"Don't be. Not like anyone knew 'bout this part o' me."

Atsumu twists them around and pulls Hinata onto his front as he glides them rapidly backwards away from the beach, smiling up at him. Hinata latches arms and legs around Atsumu. It's kind of like riding a surfboard, but smoother because Atsumu can steer them so skillfully.

Once they've made it far past the rest of the human activity, Atsumu slows them to a stop.

"Thank you for chasin' after me, Shouyou-kun." Atsumu hugs him tight. "I'd be in quite a pickle without yer help."

"Of course I'd chase after you! I'm not going to lose you, Atsumu-san."

"Even if 'm not... exactly... um. Human?" Atsumu drops his gaze, just for a second, and it tugs on all of Hinata's heartstrings. He frowns.

"Well what about you?" Hinata challenges. "Is it okay that I'm not a fish person? I mean, a seafolk? That I'm human?"

Atsumu smirks, and shakes his head. "My feelin's won't change, Shouyou-kun. I love ya just as ya are."

Hinata bonks their foreheads together, and grins. "I'm the same, Atsumu-san. I love you a lot, and want to know all about you, gills and tail and all."

"Even horns?"

Hinata's eyes widen. "You've got horns?!"

Atsumu grins and sticks his tongue out, and Hinata knows he's being fooled.

"Gah! Don't tease me like that!" Hinata laughs, tickling Atsumu's ribs under the water and making him squirm.

Atsumu laughs aloud, wiggling this way and that.

"Cheeky little..." Atsumu murmurs, then captures Hinata in his arms and shuts him up with a kiss.

"I was being serious, Atsumu-san!" Hinata huffs between kisses, holding Atsumu tight. "I want to know everything about you."

Atsumu hums agreement against his lips, and the kisses

become more sensual, more enticing.

"Okay, Shouyou-kun," Atsumu whispers, kissing his cheeks and nose. "We've got some time together before dark when the beach closes an' everyone packs up. Can't change back before then... Wanna see more of what I can do when I'm like this?"

Hinata nods excitedly. "Heck yeah!" Atsumu's smile and hooded gaze make Hinata swallow.

"Found a tiny island not too far out from here," Atsumu says. "How long can ya hold yer breath? I can get us there faster if we go underwater. Shouldn't be uncomfortable, won't go too deep."

"I don't think I've ever timed it, but I can hold my breath a decent amount I guess. Can I signal you some way if I need air?" Hinata asks.

"Of course." Atsumu twists and goes lower in the water so Shouyou is behind him. "Hook your hands around my shoulders."

Hinata complies, reaching under Atsumu's arms to curve his hands around the front of his shoulders. He puts his knees where he had them last time and Atsumu nods.

"If ya need air, just squeeze yer hands twice. 'Kay?"

"Got it!"

Atsumu turns his neck to look at him, and frowns.

"Forgot to tell ya to grab goggles. Well, just keep yer eyes closed, Shouyou-kun. Don't want anythin' in the water t' hurt ya."

"Oh, I didn't think of that either," Hinata sighs. "I'll keep my eyes closed. What about you, though?"

Atsumu quirks one side of his mouth.

Then he blinks and reveals a secondary, near-transparent membrane that coveres his eyes. Through it his irises look blue as they sky. Hinata's dazzled by them.

"Ready? Take a deep breath."

And just as Hinata does so, Atsumu dives below the surface, carrying Hinata with him.

@threadreaderapp unroll please :)