Lawli: Yes, it's another Future Fish AU where Haruka is a merman. This AU has consumed me. Merman Haru is life.

One difference is that Mako is not a fireman.
Okay, there are other differences too, but that's one of the mains.

Hope you enjoy. I'm planning on a MakoHaru endgame, but this story is evolving as I write. So I'm not sure about other pairings yet.

"It's an impressive tank, Matsuoka-san," Makoto said, staring in awe at the 4,000-gallon monstrosity that dominated the room. The tank had been installed earlier in the week, and had now been outfitted with bright pieces of coral and vegetation to simulate a natural reef. "Though I'm not sure what you're expecting to put in there."

Matsuoka smiled, thin lips stretching up to reveal his conical, slightly crooked front teeth. His eyes were bright with excitement and Makoto could tell he was eager to divulge just what exactly he planned to house in the unnecessarily large tank, but still he drew the moment out. "Take a guess."

Makoto frowned and brought a finger to his chin. He walked the length of the tank up to where it curved toward the back of the room and then stopped. In his mind he'd conjured and dismissed several ideas, the tank too large to make sense for any of them. "Dolphin?" He guessed. Matsuoka had kept dolphins before, usually ones in transition to aquatic centers. When Matsuoka only shook his head, he tried again. "Shark?"

"Much greater than that," Matsuoka said. "I told you of my newest research project, didn't I?" Makoto did not know what that had to do with whatever sort of marine life the tank was for, but his veins thrummed with the excitement of the mystery, an echo of the excitement in Matsuoka's eyes. Matsuoka continued, "I need your word I have your cooperation in it."

"I already said you could count on me, Matsuoka-san. Though I'm still not sure how I'll be able to help. I'm hardly qualified, I didn't even graduate-"

"Formal education has nothing to do with it," Matsuoka disagreed. He laid a hand on Makoto's shoulder and gave a reassuring squeeze. "You're smart, Tachibana-kun, no matter what you might think about yourself. And more than that, you're a good person. Trustworthy, empathetic. It's what makes you a good teacher."

Makoto flushed under the praise. "Thank you, Matsuoka-san, but I still don't understand what you need me for."

Matsuoka clapped him on the shoulder, and Makoto couldn't help but think the man looked just like his son when he grinned like that. "Come back tomorrow," Matsuoka instructed. "I'll explain everything to you then."

Makoto took one last glance at the tank, watched a small school of colorful fish dash across the tiny sand bed to the privacy of the tall sea grass swaying lightly in the artificial current, and his stomach flipped as he imagined what he might discover when he returned the next day. Whatever this project was, it seemed important. Not only had Matsuoka come to request his assistance personally, but his son Rin had also taken to pestering Makoto about accepting the position on a nearly daily basis. Although he couldn't fathom what the project entailed, much less how a preschool teacher could be of any assistance, the look on Rin's face - joy the likes of which Makoto hadn't seen since before Gou's diagnosis - had been all it took to sway Makoto.

He left the possibilities for the morrow as Matsuoka led him from the room with the tank up the stairs to the basement floor where the elevator reached its final stop. Another question: why the sub-basement for the tank? Most people didn't know it existed, it's access only granted by those with special key cards and fingerprints in the building's computer system. It was a storage space for waste and biohazards. Makoto could only assume that whatever had Matsuoka this elated had the potential to be extremely dangerous - possibly even deadly.

The ride from the basement to the reception floor was brief and silent. When the elevator doors slid open, Makoto was surprised to see Rin standing with a hand already raised in greeting. Off-duty from work, Rin looked out of place in the polished glass atrium with his loose track pants and hoodie, but his easy charm made his wardrobe easy to overlook.

"Did you see it?" Rin asked, after greeting his father more formally than Makoto. Makoto did not miss the flash of wry irritation - probably at Rin's state of dress - that melted quickly into warm affection on Matsuoka's face. "Isn't it huge!"

Makoto assumed he meant the tank. "Yeah," he said, laughing a little. "Matsuoka-san could probably fit a quarter of Iwatobi Bay in there."

"It's going to be even better than that," Rin assured, confident despite, for all the times Makoto asked, Matsuoka never even told him what the tank would hold. "You'll see tomorrow."

They both would, Makoto supposed, and hoped whatever it was wouldn't be a let down for his best friend. "You'll be overseeing the delivery?"

Rin nodded his head. They bade a quick farewell to Matsuoka, who'd informed them he had further arrangements to secure for the big day tomorrow. "Me and Sousuke have arranged for a small escort. We don't want to draw too much attention, but father says it's too important to travel without protection," Rin explained as he and Makoto made their way to the front doors. He paused just before the pristine glass to nudge against Makoto's calf with his knee, a teasing habit of his since childhood. In front of them the automated doors held open, letting the humid summer air waft over them. "Jealous we'll get to see it first?"

"A little," Makoto admitted. "I don't get off work until five, but I promised Matsuoka-san I would stop by right after."

"Don't rush. It will have to get adjusted to the tank and everything first, and the geeks will have to make sure all the water levels are right." Rin scoffed. "And for God's sake, can you not be so formal about my dad? You've known our family since we were in diapers. He'd probably be cool with you calling him dad."

Makoto flushed. "I... don't think that would be right." Especially not at Matsuoka's company headquarters, of all places. Makoto had too much respect for the man to address him so informally.

Conversation lulled as they followed a familiar trail to a cafe four blocks away, but just as in the elevator with Matsuoka, the silence was amicable. Rin was Makoto's oldest friend, and sometimes words need not be shared between them. Rather they flowed through an invisible bond, felt rather than heard, and understood just as well as if they'd been shouted. Beside him Rin was content, and Makoto didn't even think his friend was aware of the little smile on his face as they walked.

"Welcome, welcome," an enthusiastic voice greeted as they entered the quaint little shop nestled between two larger office buildings.

The walls were papered in cheerful pinks and yellows. On the wall directly across from the door a cute penguin mannequin posed with its arms raised enthusiastically. Every week it was dressed differently – a source of amusement for shop regulars and newcomers alike – and this week it wore a bright orange spacesuit. In its hands the café mascot hoisted a blob-like pink alien. The speech bubble beside the penguin's head declared the establishment the Interstellar Penguin Café.

They used to come to this café all the time as kids. The walls had been a little less colorful, but the same family still operated it now as did then. It had been the youngest son, who'd started off as a clumsy part-timer bussing tables, who took over for his retired parents. Hazuki Nagisa, a bubbly child who'd grown into an even bubbler adult, was a year younger than Rin and Makoto, and his unfaltering spirit and optimism the exact thing needed to rescue the café from it's steady decline.

Over the years Makoto had seen the place grow, and now it was rare find the café without a large line. Customers of all ages were drawn to the cutesy absurdity that so perfectly reflected Nagisa's character. Teenagers thought it was a cool place to hang out because there were some retro video games along the walls, and children came with their parents, attracted by the bright colors. Even a lot of businessmen and women were regulars, if only because of the café's convenient proximity to their workplaces.

"Officer Matsuoka - oh, and Mako-chan, too! I haven't seen you in a few weeks."

"I'm off duty," Rin said, taking a seat at their usual booth across from the register. There were several customers in the café but the prime spot remained empty. Rin had a theory Nagisa barred anyone else from using the booth, specifically for the event his friends dropped by unannounced.

Nagisa grinned, already at work behind the espresso machine, fixing their usual orders. "Officer Rin-Rin then." He laughed at the mock scowl Rin directed toward him. "No Sou-chan today? Weird to see one of you without the other."

"Just 'cause we're partners doesn't mean we do everything together," Rin grumbled.

Nagisa set the first drink - Rin's green tea smoothie with protein powder - on the bar-top, flashing the redhead a wink as he did so. "Oho! Partners, is it?"

"You know what I mean!" Rin stomped up to the bar and snatched his drink up. He raised his fist, though the grin on his face lessened the impact of the threat. "I should clobber you for all the gay jokes."

"In my defense, you're the one providing the material."

"You should show me some more respect," Rin complained, thumping a fist to his chest. "As your elder and the guy you'd call on to protect your skinny ass."

"You're all bark and no bite, Rin-Rin," Nagisa teased. He pressed a button on the espresso machine, releasing a puff of hot steam into the air. "You act tough but we all know what a softie you are at heart. Right, Mako-chan?"

Makoto held up his hands submissively. "Leave me out of this one." The last thing he wanted was to get in the middle of an argument about Rin and his work partner's questionable relationship. While he'd never taken Rin at anything less than his word when Rin insisted he and Yamazaki Sousuke were just friends, Nagisa had always had his own suspicions, which he felt necessary to share with Makoto whenever possible.

Truthfully, Makoto didn't care if Rin and Sousuke were together (though he did worry about the strain it might put on the two officers' work relationship if they were) he just hoped Rin would be honest with him. They'd been friends for so long, the thought of Rin intentionally keeping secrets was a painful one, especially when Makoto was always so open about his own life.

"Is that Rin I hear?" A loud voice cried from the back room.

The sound of running preceded a resounding crash and Makoto, Rin, and Nagisa collectively winced. Several muttered curses later a lanky redhead staggered out from behind the curtain. His gold eyes brightened the moment they landed on Rin, who immediately dove into the safety of the booth with Makoto.

"Hi, Momo," Makoto greeted when it became apparent Rin had no intention of doing so. Rin slurped loudly at his smoothie, pointedly ignoring the boy who'd idolized him since high school. He made a face at Makoto's disapproving glare.

"Rin!" Mikoshiba Momotarou dashed out from behind the counter and bounded up to their booth in a matter of seconds. "How are you?" He was already running over the words before Rin could answer. "How is Gou? I heard – Nagisa told me – she's back in the hospital. Is everything all right? If there's anything I can do—"

"She's fine," Rin snapped, features darkening and closing off.

Makoto's expression softened and he battled the intense desire to reach across the table and cover Rin's hand with his own. The excitement of his father's tank and whatever might be going in may have lifted Rin's spirits a majority of the day, but now he'd been reminded that the newfound hope (how this tank represented hope, Makoto wasn't sure) did not change the grim reality of Gou's hospitalization. "She should be released later today, as soon as her fever's broken."

Momotarou sighed. "That's a relief." He hesitated, playing with the hem of his apron. "I was wondering if I could send her flowers—"

Rin slammed his hand down on the table. "Keep the change, Nagisa," he said, before storming out of the café. The bell on the door chimed merrily behind him.

Makoto, Nagisa, and Momotarou stared at the crumpled notes - more than enough to cover both Rin and Makoto's drinks - in surprise, and then Momotarou sagged into Rin's vacated half of the booth. Makoto offered him a sympathetic smile. "I'm sure she'd love flowers," he said encouragingly as he rose to his feet. Momotarou brightened, but only a little. "Nagisa, I'm going to go after him."

"But your coffee," Nagisa started to protest.

Makoto glanced over his shoulder on the way to the door. "Give it to Momo!"

Having a best friend with an affinity for vibrant hair dye always made it easy to find him in a crowd. Makoto spotted Rin moodily crossing the next street within seconds even with the moderately heavy pedestrian traffic. Makoto sped up to a jog, and quickly was able to catch Rin by the elbow and turn him around.

Rin glared up at him, angry tears dancing precariously at the corners of his eyes. Makoto opened his mouth to say something but Rin cut him off before he had a chance. "Spare me the pep talk, Makoto."

"That predictable, huh?" Makoto smiled. "Actually, I wanted to make sure you didn't forget this." He held out the green tea smoothie Rin left behind in his hurried exit, which Makoto himself barely remembered to grab on his way out.

Rin blinked, then took the drink. He stared at it for a long moment, seeming lost in thought, before looking back up at Makoto and asking, "where's yours? Give it to Momo?" Makoto gave a helpless little shrug. "You—ugh. I didn't pay for that little shit to get a free drink. Go back and get it!"

"Rin—"

A car horn blared. Belatedly the two men realized they were in the middle of the crosswalk and that the signal had long since changed. Makoto tightened his grip on Rin's elbow and hurried them off the street, waving and mouthing apologies to the drivers behind them. Rin rolled his eyes and flicked them all off.

"Rin," Makoto scolded. "You can't just do that, you're a police officer!"

"So? They were rude."

"We were the ones standing in the middle of the road." Makoto sighed in exasperation, releasing Rin's arm at last to run a hand through his hair. "Anyways. I just wanted to make sure you were okay."

Rin somehow managed to make taking a drink of his smoothie look aggressive. "I'll be fine as soon as - whatever it is arrives tomorrow. If it can really help."

Deciding now was not the best time to voice his niggling concerns about Matsuoka's mysterious acquisition, Makoto pressed his luck on another issue. "And then maybe you can treat Momo a little better?" The way Rin began to chew on his straw made the possibility of that happening seem unlikely, but it read more as annoyance than anger so Makoto persisted. "He's not a bad guy, and he's always admired you."

"Tell him not to talk about Gou and maybe I'll be nicer."

"I think it's sweet he wants to send her flowers-"

"She's sick! It's not appropriate. She needs her family, not to be treated like some—some trophy!"

Considering Rin had been giving these same excuses long before Gou even fell ill, Makoto had the feeling it had more to do with Rin being an overprotective big brother than anything else. No man would ever be good enough for Rin's precious little sister, and she would always be too young to think about such relationships. Having a younger sister himself, Makoto understood that sentiment. His own little sister was in high school now, and he wasn't blind to how she turned heads when she walked down the street.

Still, poor Momotarou had harbored his crush for Gou for nearly ten years now. "His feelings seem genuine to me, Rin, but okay. I'll talk to him."

"It's not your job to get him in line, Makoto. You're not everyone's mother!"

Makoto's eyes widened as the words lanced through him. His gaze dropped down to the floor and he heard Rin curse under his breath.

"Fuck, I didn't mean to be a dick. I'm just... My baby sister is dying." Rin's features crumbled, the tears that had just managed to subside returning to flood down his cheeks. "Gou is dying."

The sting of Rin's words immediately forgotten, Makoto threw his arms around Rin, pulling the shorter man against him. Rin did not fight the embrace, instead his arms reached up to grasp Makoto's shirt. "We're going to help her," Makoto promised. "Whatever it takes, whatever we have to do."

Whatever Matsuoka's discovery was, Makoto prayed it really would be able to help Gou.

Not just for her sake, but Rin's as well.

At work, Makoto found it hard to concentrate. Problematic considering his students demanded constant attention. Four-year-olds were prone to getting themselves into ridiculously hazardous situations if left to their own devices, as testament by the numerous accident reports that piled up in the preschool's front office on daily basis. So Makoto shook himself whenever he found his thoughts wandering to Rin or Gou or the sub-basement tank, and got himself through the day's art projects, phonics lessons, the messiness of lunchtime and temper tantrums of students who did not want to settle down for their afternoon nap, and eventually made it to 5:00.

Admittedly he rushed with his classroom cleanup a bit, but the floors and tabletops were all sanitized and surely anything he might have missed could be saved for the morning. He bade hurried farewells to his coworkers and took off before any of them might stop him for a chat, all but running to the bus stop.

The bus took him to the subway station, which carried Makoto downtown. Makoto wished for the days when he and Rin lived within spitting distance of each other, and any cool new toy or treat could be showed off or shared by merely passing it from one bedroom window to the next.

Security was tight, Makoto noticed straightaway as he approached the Matsuoka building. Right as Makoto stepped through the automated doors an officer approached and asked for his identification. Makoto fished his wallet out of his pocket and flashed his driver's license.

Before the officer could ask to examine the card, a soft voice interrupted, "he's on the list."

The officer glanced to the approaching petite figure and back to Makoto. The young woman, with bobbed silver hair and kind blue eyes, came to stand beside them, a badge in her hands.

"Tachibana Makoto," she said, holding up the badge. "He's on the list."

Makoto took the badge, which showed a picture of himself, his name, and some code meaningless to his uninformed eyes along the bottom, and slipped the lanyard around his neck. The officer gave him an approving nod and made his way to the next person waiting to gain access to the building. "So you're here too, Nitori?"

Nitori nodded quickly, turning toward the elevators. Makoto followed. "I've been involved with the project for a few months now. It's all been very hush-hush," she explained once they were inside the elevator car. "Rin-senpai didn't even know until today." Ten years after high school and a PhD under her belt and she still called Rin 'senpai.' Some things never changed. Makoto smiled. "I felt horrible keeping that secret from him, but it was for Gou-chan's sake. He wasn't happy but he understood."

"Rin's seen it, then?"

"Yes, this morning." Makoto hummed under his breath, shifting on his feet. Nitori took notice and raised a questioning brow at him. "You're nervous."

Makoto scratched at his elbow. "To be honest, I'm not really sure what I'm getting myself into here," he admitted. "I don't suppose you could tell me?"

Nitori shook her head solemnly, but a wistful smile had wormed its way onto her face. "It is indescribable."

Indescribable, she said.

She could not have chosen a more appropriate word. Because the sight that greeted him as they entered that cold sub-basement room, after swiping their ID badges and performing their fingerprint scans, was beyond fathom.

It drew his focus immediately, even with the surrounding commotion competing for attention. Men and women in white coats like Nitori, scribbling notes or tapping furiously at computers, or adjusting dials on the multitude of machines that lined the walls... They all faded into the background as Makoto's vision narrowed on the creature curled defensively at the bottom of the tank.

"What in the world..."

Makoto's feet carried him forward, and before he knew it he stood in front of the tank, nose practically brushing the glass as he strained to get a better view. Not much more than the great blue tail was visible at this angle, curling out from the tangle of seaweed planted along the bottom of the tank, but Makoto could tell the creature was large. The tail was thick, and probably measured a good two yards, but it definitely didn't belong to any sort of fish Makoto had ever seen.

Hoping to see more he started to move to the left to where the tank began to curve back, but Rin impeded his path.

"Amazing, isn't it?"

Makoto shook his head, awed despite not even having seen the creature in its entirety. "What is it?"

"There's no species name for it yet. It's the first of its kind – hell, the only one on if it's kind for all we know," Rin explained. "Around here they're calling it Ariel."

For some reason, calling the magnificent creature by such an obvious name struck Makoto as wrong. "That's so impersonal."

Rin laughed. "It's not a person, Makoto. It's barely even sentient. Geez, sometimes I really think you're too soft for your own good."

Makoto conceded, glad at least they'd given Ariel more than a mere number for identification. They moved around the tank so Makoto could finally get a better look, and Makoto gasped as he spotted an arm poking through the seaweed, and then another. In fact, a whole torso was hidden behind the lightly swaying grass, completely human except for where it attached to the glittering blue tail.

"How is this real?" A creature half human and half fish? That sort of thing only existed in fairytales – or, at least, it should.

A head popped up suddenly, half obscured by long dark bangs. As the current drifted through the tank, the creature's hair fluttered out to the side to reveal impossibly bright blue eyes. They hooked on Makoto and the long, narrow pupils dilated. Ariel tilted its head to the side, mouth falling open but releasing nothing more than a few bubbles.

Spellbound, Makoto drew closer. He raised a hand, pressed it gently to the tank, and waited, hoping Ariel might swim over to investigate.

No one expected the creature to lash out

Teeth and talons that had certainly not been there a few seconds ago were suddenly bared, the pupil's of those too-blue eyes narrowed to catlike slits as Ariel suddenly threw itself against the side of the tank.

Despite the many thick layers of glass separating him from the creature Makoto reflexively jumped back in surprise. Rin pulled him the rest of the way back, and distantly Makoto heard him asking if he was all right. The room dissolved into chaos. Scientists wrestled Rin and Makoto out of the way, half wanting to observe this unexpected change in behavior and the other half intent on calming things down again.

Makoto noticed Nitori aiding a tall bespectacled man with injecting a clear liquid into one of the many tubes feeding the tank water. It was a viscous substance, easily recognizable when it hit the tank and began to spread out and slowly dissolve. Ariel looked up at the top of the tank, anger flashing across its startlingly beautiful features, but then its expression froze. Strangely lifeless, it fell to the bottom of the tank and did not stir again. Although forced into a state of paralysis, Ariel retained the movement of its eyes, and it was quick to locate Makoto amongst the crowd.

Maybe it was coincidence, but Makoto didn't think so. There was no distance in Ariel's eyes, no drugged haze. Ariel found him intentionally, perhaps because for whatever reason he'd been the one to illicit a violent reaction from the creature. Regardless of the reason, Ariel's eyes did not stray once they landed on him.

Rin said the creature was barely sentient, but already Makoto could already tell that was a lie – either one fed to him by his father and the scientists or by the creature itself playing at incomprehension. The piercing blue eyes locked on his were anything but unintelligent, and the longer he remained under the gaze both furious and completely helpless, the more cold apprehension slithered down to the pit of Makoto's stomach.

What had he gotten himself into, indeed?