Archive of Our Own ^beta

Chapter Text

Three months.

It’s been three months since Atsushi was kicked out of the orphanage, and things have never seemed so dim before. The white-haired orphan travelled around the chain of islands from boat to boat, after asking kindly to the ship’s captain or simply stowing away.

The islands that made up Yokohama were scattered among a large body of water, one that could not be classified strictly as a “lagoon” or a “lake. Because of a series of recent events, the water levels was fluctuating at a fast and unpredictable rate. Something scientists and sailors alike could not explain. This lead to only one explanation; the rapid rise and fall of the ocean’s tides was caused by a mythical.

A mythical was a term to describe someone who wasn’t just human, but something else. Something people have grown to acknowledge, but remain unaware of its origins. They were the things that borne fairytales and fables. Anything that defied the laws of reality, or was incomprehensible, was mostly likely the works of a mythical. Those with fabled abilities who stir up trouble are handled by the ADA.

With the full moon approaching, many sailors were finishing up their business early, for none wanted to get caught in one the of the water’s shifts. These times were dangerous to travel in; several small cargo ships had already been capsized. No one drowned, and the people aboard the ship didn’t suffer too bad of injury, but it had shaken up the entirety of Yokohama. The drastic change in the ocean happened once in awhile, on the night of a full moon.

It was at the west shore, where the two ADA detectives found the white-haired young man, staring off into the foggy waters of Yokohama. All the business located near the shore closed up shop early and took with them anything of value, in fear the waves would steal them away. The beach was deserted, with the locals going more inland and for higher ground.

“What’s a young lad doing alone at the beach on the night of a full moon? Don’t you know that the sea has become frisky on nights such as this?” The hazel eyed detective wondered aloud, taking Atsushi out of his daydreaming. The lad’s gaze travelled to the two detectives, and widen at their presence. He rose from his spot by the bank, and dusted the grains of sand clinging to his threadbare clothes.

“I- I was looking for something.” he hesitated. Stealing a quick glance at the water, Atsushi fiddled with the edge of his shirt.

“What would be so important to look for on one of the most dangerous nights of the month?” Kunikida inquired, eyeing the young man skeptically.

“You would think me crazy,” Atsushi paused “but I feel like I am being followed. By something in the water. Every so often, when I dare to near the water, and look at the surface, I would not see myself, but something else entirely.”

The curly haired man hummed, and casted his partner a look.

The orphan continued. “In my dreams, it come to the surface and pulls me down with it. It was been following me for weeks.”

“Sounds like an awful death: one with a strange creature to drag you the depths of the sea. Never to be seen again !” Dazai tapped his chin in thought, stars in his eyes. Kunikida wrote the story down.

“We believe that the odd behaviors of the ocean to be the work of a mythical,” the bespectacled man continued to scribble in his pocket-sized notebook. “Your story matches with what intell we’ve gathered from other locals. We need your help in catching the mythical.”

The orphans sunset eyes all but popped out of his skull. “I-I couldn’t! It’s been chasing me. You’ve seen what it’s done to boats !”

“Now, now, Kunikida -kun~~, that’s no way to ask a favor! Especially from a frightened, lost soul!” Dazai shook his head theatrically, feigning exasperation. The suicide-maniac strolled over the Atsushi, “I’m Dazai, famous and all-powerful detective who’s in search of a lovely lady to commit double suicide with!” He threw a friendly arm over the orphan’s bony shoulders.  “What’s your name?”

The young man jerked to the sudden weight leaning on him. “... Atsushi Nakajima.”

“Atsushi -kun it is! Say, Atsushi- kun , help us out and Kunikida here will treat you to whatever your tummy desires.” And with impeccable timing, the orphan’s abdomen did it’s best impression of a dying whale. Atsushi flushed and quickly muffled his stomach’s growling.

Atsushi thought to himself, ‘ When was the last time I ate? And how long will it be until my next meal? Helping them wouldn’t be too much…’

The white haired teen offered a weary smile, “ I guess it wouldn’t be too much trouble to help? And it would help a lot of people…”

And before Atsushi knew it, he had eaten seven bowl of ochazuke , and now stood on the sands of a different beach. He hadn’t been there before, but the view was beautiful: with no boats prompting small ripples in the surface, the sunset reflect vividly off the water. There was no noise of the town, only the soft waves dancing againsts the shore, the chirps of birds and the two detectives quiet chatter not too far away.

With the setting sun, Atsushi felt strangely calm, despite the danger of being easily pull in the water by a creature, just like in his dreams. Soon only the stars were left, and the moon quickly coming from behind the horizon. Dazai and Kunikida’s voice grew too soft to hear, only the tide’s dance upon the shells and grains of sand could be heard.The full moon rose into the sky, shedding its lights down onto the close knit islands of Yokohama. Atsushi’s eyes became dim as he stared unblinkingly at the moon. His feet dragged towards the water.

“Atsushi -kun ?” Dazai called out, but the orphan didn’t flinched.

Atsushi was up to his knees in the frigid sea when he finally heard Dazai’s shout of his name. But it was too late.

Circles composed of glowing white characters engulfed Atsushi’s form. He felt his legs grow too heavy and weak, and fell forward as tiny scales spawned across his skin. Atsushi sat in the water as his tail curled around him, unmoving.

The two detectives held still, surprised. They had expected Atsushi to be the source of the tides’ changes, but they were not prepared to deal with a siren.

“...Atsushi -kun ?” Dazai called out, ready to defend if necessary.

The siren looked over at the sound of his name. His pupils had become slits, his arms were wrapped tightly around him as he shook. The waves grew agitated in response. Spheres of ocean water rose from the surface and were flung towards the detectives. “Guess it’s time to wrap this up.” Dazai muttered under his breathe. He sidestepped Atsushi's orbs and trudged through the stubborn waves. As he came closer to the siren, Atsushi hissed and recoiled.

“Shhh, it’s just me, Atsushi -kun .” Dazai cooed as he collected the orphan is his arms. Atsushi struggled at first, but as the curly haired detective activated his fabled ability, his eyes rolled back and Atsushi went limp in Dazai’s arms. The sea calmed immediately after.

Kunikida, who was now soaked through his clothes, cleared his throat and wrote in his notebook. “Well, that solves one issue.” He concluded.

Chapter Text

The two mythical detective chose split up; with Atsushi unconscious, and not as threatening in the ocean, Dazai could held him alone, and Kunikida could change his clothing and report the recent developments to the director.

They went their separate ways. Dazai with Atsushi wrapped comfortably in his trench coat, his ivory legs dripping with sea water, and headed towards one of the nearby ADA safe houses. Thankfully, no one was around when he climbed up the stairs to the second floor, and no one saw his brief struggle with unlocking the door. All the while, the orphan mythical was sound asleep.

While filling the bathtub, Dazai placed Atsushi down on the bed, and searched around the safehouse for food. He found an unopened box of crackers and took them to the bathroom. The tub was filled near to the top. Atsushi was carefully lowered into the water and seemed to relax at its touch. The curly haired man nodded at himself with satisfaction. He left and quickly returned with a chair, then locked the door behind him.

An hour later, Atsushi roused in the water. His slit-pupiled eyes lazily wandered the bathroom ceiling, until setting onto the detective’s sleeping form. The curly haired man had his arms crossed and his head leaning back on the chair. The siren tensed with a quiet hiss, but when Dazai didn’t react, he settled down, still alert.

Atsushi continued scanning the bathroom, curious. When he saw a large sea shell sitting on a shelf by the tub, he picked it up for closer examination. He held it between his sharpened nails like it was the most fragile thing on earth. As he stared at the shell, he felt tiny glimpses of memories rise. The beaches. The boats. Fear. Running. And a voice, too cheerily for the gloom of the beach. The detectives.

In silent alarm, Atsushi remembered the full moon and the his shifting. He looked at his hands and saw his nails at a short point, with pearl white scales speckling his arms. He lifted what he thought was his lefts and saw a long tail. With blurry, tiger-like stripes,splashes of gold, and purples sprinkled around, willed it to move. It flopped back into the water with a large splash, pulling the sleeping detective from his nap.

“Dazai-san.” Atsushi’s voice echoed against the tile walls. “What’s happened to me?”

The suicide maniac felt wide awake, and rubbed the remaining sleep from his eyes. “You transformed under the moonlight, Atsushi-kun. You’re a mythical.” He pulled the chair closer to the tub. “What do you remember?” Dazai couldn’t help to steal a good look at the siren, he couldn’t see much in the evening moonlight and the ocean’s water.

“I… was at the beach. The sun had just set. When I saw the moon, I felt tranquil. But when I saw you and Kunikida-san, I felt scared. I thought you were going to hurt me.” he was gaping at his hands, still shocked at his change in form. “I guess what I saw in my dreams was true… kind of.”

“Why did you think Kunikida and I were going to harm you? We had talked before.” Dazai thoughtlessly reached over, and tucked a black lock of hair behind Atsushi’s ear fin. The siren shyly looked away.

“There were people hunting for me, in this form. They thought sirens could heal the near-dead.”

Dazai hummed in response. “Well, do you know how to change back?”

Atsushi’s cheeks reddened. “I’m not sure, but… I need clothes.”

Dazai stifled a chuckle and pulled the plug to drain the tub. “Right, I’ll see what I can find. Let’s get you dried off first, hm? Maybe that will help you back to human form.” With the towels from under the sink, Atsushi patted down his shimmering tail, while Dazai called dibs on drying his hair. Free of water droplets, Dazai lifted the orphan like a princess, sending an unprepared Atsushi to hold on to his shoulders.

Sitting on a towel on the bed, Atsushi patiently waited while Dazai shifted through the save house’s closets. “Don’t go anywhere.” the detective joked. The siren rolled his slit eyes, and readjusted his tail to fold towards him, like he was hugging his knees. He thought being dry as a siren would be painful, or uncomfortable, but Atsushi felt no difference between sitting like this and sitting while in human form. But, the longer Atsushi was dry, the faster his scales were retracting back into his skin.

By the time Dazai returned with shorts, Atsushi was scrambling to cover himself.

“I found some short-” Dazai froze at the sight of pale, slender legs. He quickly decided to examine the beauty of the ceiling, tight lipped as he tossed the other mythical the clothing. “T-Thanks.” he heard, and quick shuffling of fabric. The detective tentatively  peeked down. Atsushi was now a little more decent. He was shivering from cool air of the safe house, so Dazai tossed his now-dry coat over his shoulders.

Atsushi gave a smile in appreciation as he pulled his arms through the sleeves. He rose to his feet cautiously, small patches of scales up his legs. Atsushi stood unsteady, in only his coat and a pair of shorts. Dazai bit his cheek.

“Atsushi-kun, you should join us at the agency.” Dazai said out of the blue.

The siren shifter tried to walk, to see he had grown used to his legs so soon after changing back.

“Hmm? Why is that?”

Atsushi’s knees buckled. He leaned onto Dazai, one hand on his chest to steady himself. The siren shifter flusteredly raised his head to apologize, but froze Their gazes held each other, Atsushi lost in the endless voids of chocolate cake batter, and dazzled by the specks of gold that sprinkled around outer edge of the iris.

Dazai was tracing every slope and curve of smooth pale skin, dazed by the tiny freckles he didn’t see before. His eyes traced over every detail of his faces, and ended on Atsushi’s lips.  Atsushi’s eye flickered away from the pools of brown on Dazai’s lips, and blushed. A pale hand gentle cupped Dazai’s face, bring him out of the Atsushi-induced trance.The siren shifter lightly brushed the detective's cheek, making his ears turn red.

As the distance between the two shortened, Dazai’s gaze shifted moved to his sunset eye’s asking. Only a breath away, they were, when Dazai’s phone went off.

Ripped away from their moment, Atsushi scurried back toward the bed with pink cheeks and a fast heartbeat.

Chapter Text

In all honestly, Atsushi was expecting his past to coming catching him eventually. It just happened later than he expected, and he almost thought maybe, just maybe, his hunters have given up the pursuit based on an unproven rumor.

Hindsight is 20/20, the sunset-eyed orphan thinks. Atsushi seriously doubts Ranpo of all people to call and ask for his help directly. Through Kunikida or the director, maybe, but for the “backbone” of the detective agency to admit his navigation skills and common knowledge to be subpar, and then request Atsushi, the greenest of greenhorns of the ADA, to assist him in finding his way through the streets and whatnot, seemed laughable.

The white-haired detective bit back the panic rushing in his veins and began to strategize. There’s four crowding him in now, all armed with a makeshift weapon of sorts. The full moon is weeks away, but Atsushi can feel the siren’s pull in the back of his mind. There’s several puddles of water below his attackers’ feet, and thick clouds sailing above.

The first to strike is a gangly man with a rusted pipe swinging in both hands. Atsushi sidesteps to the right, and sends a rush of water into his face. The man chokes on whatever the water was carrying, and bends over in a coughing fit. Without a beat, Atsushi kicks the coughing assailant into the next man, but the third manages a hit to his ribs. Before the girl with the quick fists can strike again, Atsushi tumbles backward, clutching his side.

With the stress of the ambush, and now a surge of pain when he breathes to deeply, Atsushi struggles to remain calm. He can feel the scales rippling along his arms: a lapse of control is a chance for the siren to come full force, and wreak havoc-

‘But I won’t let it get that far.’ Atsushi’s eyes narrowed into slits as he pulled water from the clouds to crash down into his attackers. He dashed down the alley way.

Atsushi rounded the corner, barely missing the trash can tossed his direction. Turning on his heel, he went down the stairs towards the ocean. He pulled the water from the sea and thrusted it behind him. Atsushi could tell by the gasp of surprise he managed to hit one. With only the fourth and final assailant to deal with, he hurled a series of waves over beach, but the attacker dodges with a quick jerk. Soon, they were fighting in close quarters.

The fight seemed to last for what felt like hours, and there was not a single break in the brawl long enough for Atsushi to summon water, or create any distance between him and the other. His opponent came quick and with a bronze dagger, swiftly impales the siren-shifter.

Despite the pain, Atsushi took advantage of the small gap between him and  his attacker and pushes him to the ground. A dome of water rises and surrounds the two. Crimson ribbons twirled and dispersed into the dome, creating a slight tint. Atsushi pinned his opponent in the water the best he could, the other trying to reach for the dagger lodged into the siren-shifter’s side. Atsushi retaliated, and sent an elbow into his stomach. The attacker gasped in pain, air escaping. The struggle ceased as water fills his lungs, and the body became limp.

Atsushi released his tight grip on the dome, water bursting like a popped balloon. Without the rush of adrenaline to keep the pain at bay, he crumpled to his knees, grasping at the wound. He reached for the blade and pulled, but retracted his grip with a hiss. The blade was pure iron and had teeth on the spine, causing flesh to be ripped at it was being pulled out. With his vision blurring at the edges, he fished out his phone from his back pocket.

It was for times like these that Atsushi was glad to have invested in a waterproof case for his phone. He was punching in the numbers for speed dialing the agency when he found himself teetering to the side, and the world became dark.

Long fingers carded gently through silver strands. Soft humming drags Atsushi from the darkness, and he opened his eyes. He winced at the harsh lighting and blinked to readjust.

He was laying down on a large bed on his uninjured side. Dazai is sitting next to him, his trenchcoat over the back of a chair. In one bandaged hand, he held a book titled ‘A Hundred and One Lovers’ Suicide’ , and in the other, he tangled around Atsushi’s hair. Dazai leans the headboard, murmuring a catchy song from the radio. The curly haired detective seemed very invested in his reading, and doesn’t notice Atsushi’s watching eyes until he reaches to turn the page.

“Ah, Atsushi-kun, you’re awake. How are you feeling?” He sets down the book, dog-ear folding his page. Dazai tossed it on the night stand and feels for the siren-shifter’s forehead. Cold fingertips skimmed against fevered skin.

Atsushi gingerly sat up to meet Dazai half way, holding back a grimace.

“It’s pretty chilly in here, you were burning up earlier.” Dazai flipped his hand over and tried the palm of his hand. The younger of the two simply nodded in agreement. Shifting closer, Dazai gentle held Atsushi still is he pressed his cheek to his forehead. Atsushi froze in surprise, his eyes widen at the close contact.

“...Dazai-san…” the siren-shifter felt fatigue crawling up his limbs. The older of the two gave a giddy grin. He climbed back upon the bed and resumed his place before Atsushi awakened. He softly pulled Atsushi down and rested his head in his lap. Atsushi went to protest, but was soothed into relaxing when Dazai continued running his fingers through his hair.

“You had us scared for a moment, Atsushi-kun. Yosano was considering killing you back to life, if we had not seen your chest rising.”

The former orphan reached for his wound, and was relieved to find the blade removed. A large square bandage covered his side, with wrappings around his torso to hold it in place. He gingerly touched the center, and recoiled at the burning sensation that stretched across his frame. Dazai softly pulled his hand away from the wound.

“Sleep, Atsushi-kun, I know my lap is the comfiest around.” he joked. Unable to hold back the spreading heat from his face, Atsushi gaped like a fish out of water. He quickly reigned himself in, and let his eyes close, and drifted asleep.

Chapter Text

“Are you ready for the full moon?”

“I feel better prepared, if that makes  sense.” Atsushi sat at the edge of the salt water pool, watching the birds fly off in the water’s reflection.

His curly haired mentor of sorts was leaning against the guardrail of the roof’s pool, the ones made to keep people from falling over the edge. “At this height, I wouldn’t even die ! Only suffer, in agony , at gravity’s and Yosano’s hand~!” He mentioned the first time they went to the highest level the stairs could take them. The roof provided a stunning view of the islands at sunset, the light bouncing off the ocean just at the right moment to make the islands appear as if they were floating in the air.

The young man was always a bundle of nerves are the night of full moon came, but calmed down as the moon ascended. The circle luminous letters spawned around his body, and without struggle, he slipped into the water. When Atsushi came back to the air, his slit eyes would dilate as he gained control over himself. For the rest of the night, he would drift around in the pool until he tired, and when would sleep beneath the moonlight.

Dazai always found Atsushi’s metamorphosis beautiful, not that he would ever admit it aloud. He allows found himself volunteering to keep an eye on the siren, helping him gain control of his fabled abilities, or breaking him free from a lunar trance. Though some would say it was his commitment to do so, as he brought Atsushi into the agency, Dazai never felt “burdened” for guiding the siren. Atsushi was an interesting mythical; he seemed more human than some of the full-blooded monsters in human’s skin seemed to be, and then some. He was full of surprises, ones that people least expect but hope for the most.  And of course, Dazai had his own reasons of spending so much time alone with Atsushi, for reasons he’ll never say.

Atsushi swam towards the edge of the pool, and rested his head in his arms. He was humming to himself quietly, his tail swishing lazily behind him.

“Dazai -san , are we even allowed to be up here.” Atsushi looked in his direction.

Plopping himself close to the siren, the hazel-eyed detective offered a mischievous grin. “We’re allowed, so long as we don’t get caught~.”

Atsushi rolled his eyes, and slithered underwater. He came back up with a strong push of his tail, and caught his torso above arms with his arms, lifting himself to sit next to the lunatic.

With have strippinig down and wrapped in a towel for the changing, it had given Dazai a perfect view of Atsushi’s scar. It had crawls across his pale skin with ivy, only a slight discoloration remained. Dazai traced over the raised skin with his index finger. The siren shifter had grown used to the detective’s caresses  over the scar from months ago, and if anything he leaned into his touch.

“It doesn’t hurt anymore?”

Atsushi stretched his arms high. Dazai shamelessly watching the his muscles flex as the siren-shifter lazily wade his tail in the salt water.

“Not anymore, but it is a bit sensitive. You’re not hurting me, Dazai- san .” the brown-eyed man nodded in response, watching Atsushi bite his bottom lip when Dazai’s fingers grazed against the center and most tender part of his scar.

Atsushi tried to hold back a moan, but a pleased sigh escaped his lips.

The detective’s fingers froze, his pupils widening. With a shit-eating grin, he poke the same spot again. The siren shifter lets out a heavier sigh, and catches Dazai by the wrist. He yanked the detective close, “Dazai-san, please don’t tease me.”

But pupils are blown wide and heart beats, accelerated. Atsushi releases his wrist and slowly runs his fingers through curly strands, careful of his nails. He pulls the detective forward, and presses their lips together for a chaste kiss.

Just as the they pulled away for air, Dazai pushed Atsushi over and claimed his lips once more.