A/N: Hello! I had taken a break from writing all together for a while, but Reigisa has recently become a love of mine, so I just had to write a typical mermaid AU. I hope my writing isn't too rusty, and I hope you all enjoy where I plan to take this story!

Rei Ryugazaki was not known to have a deep passion for much else than the beautiful things in life, running, and science. It was not unusual for colleagues to collectively look at Rei as he muttered to himself during the science labs in school. He was the last to go, but oddly enough, the first to finish his lab reports. When confronted about why he stayed and worked on something new, or spoke to the teacher about something published in a scholarly journal, he would simply reply with a gentle smile that he just enjoyed it. Theories, calculations, mysteries of the universe that couldn't be explained - all of it was wonderful to Rei. Why theories were theories and how laws were laws. He could stay at night for hours wondering how life began, the separation of the body and the mind. Why life existed at all, and how beautiful it was that it did.

He loved his studies. He truly believed that.

But sometimes, when his friends would ask if he was happy, he often later thought about his lie, when he gleefully said yes.

And sometimes, when he was out on his nightly jog across the beach, he thought about how much longer he could keep this up. Theoretically, his life was wonderful, and he knew that. His high school friends Haruka Nanase and Makato Tachibana and himself all shared the rent in a little (but very quaint and pretty) house by the ocean. They all had fun together with little financial issues, small amount of light quarreling at home, strong bonds, no one in his family had died - So why? Why did it feel like something was missing? Why hadn't he gotten any sleep for the past two days and why did it feel different to go home? The feeling nagged at him on this particular night, and caused him to gradually slow down until he stopped by a few boulders, and he leaned against them, catching his breath. He didn't look at anything, and he felt very little.

Why weren't his friends good enough to cheer him up and why did he fail his last lab test and why did he suddenly hate school and why did nothing feel familiar?

All he could do was breathe, and sadly, this feeling was becoming an old friend. The feeling that he knew that sometimes, all he could do was breathe. All he could do was match his breathing to the monotonous sound of the waves drawing inward and outward.

He soon laid himself down, perfectly positioned so that his head was placed just on the border of where the water and the dry sand met. He spread out his arms so he could feel the rush of cold water lap at his skin.

"There is scarcely any passion without struggle," he said softly to himself. Facing the stars, all he could think about was space, and the existence of humans, and if his place on the Earth meant anything. There was a whole great big universe out there, and Rei Ryugazaki felt as if he was just a spec, floating along. There were nebulas exploding in the powerful, vast darkness that was space. Molecules and atoms colliding and rearranging matter.

"They're really beautiful, aren't they?"

Rei shot right up, so quickly that his glasses almost flew off. He scrambled to his feet, turning to see what had spoken behind him. He'd sworn no one had been around him, but what he saw before him, well, almost made him laugh. Scratch that, Rei did laugh, hard. The person before him began to frown.

"I'm sorry, I'm sorry," he began, "it's just that.. Well, isn't it a little early for Halloween?"

Before him was a spritely looking blond haired boy around his age, laying in the sand with what seemed to be a light orange mermaid costume. He had a remarkably youthful face, with eyes as shiny as his costumed scales.

"I do have to say, that's an impressive costume." He adjusted his red-framed glasses as he stepped forward. Placing his hand under his chin, he hummed as he observed what appeared as such a seamless and smooth transition from human flesh to shimmering scales.

His guest began to move himself backward just as Rei moved closer. "Oh, sorry, is it okay if I look closer?" Rei thought it was a bit weird for the boy to be so scared of him.

His visitor looked at him worriedly, then away. After a pause, the boy asked, "You're… good, right?"

Rei furrowed his brow before smirking. "Well, yes. At least, I think so." Maybe he asked if he was good at something? Rei briefly wondered if his visitor was a little inebriated. Deciding to humor his guest, he asked, "Are you?"

The blonde boy's demeanor changed, and there was a hint of a smile. "Of course! My name's Nagisa. Nagisa Hazuki, actually. I've seen you… what was the word…" He trailed off, scratching the side of his face with his finger before snapping his fingers. "Jog! That's the word right? I can see you from way out in the ocean. No one else really is visible at night. You usually don't stop though. Are you okay? I swam up to check on you. You look really beautiful when you jog! Where are you going?" The boy showed no embarrassment about calling Rei's running 'beautiful', and continued to flash a bright and curious smile.

Rei took a few steps back. "You watch me jog? Just who are you?"

"Nagisa! I just told you that."

Rei looked around him, but the rest of the beach was dark and secluded. "How did you get close to me without me noticing?" He posed this question to himself as well. He usually wasn't one to be taken off guard.

"I swam up here? I just told you that, too! Are humans always so dense?" Nagisa scratched at his head, laughing.

"Why are you out this late anyway in a costume like that?"

Nagisa returned to his puzzled look. "Costume?" He looked down at his tail, then back to Rei. He raised it and waved the seaweed textured fins around. "Are you talking about this?"

Rei stood, both taken aback and a little surprised. "You have a lot of control over it, considering it's just plastic..."

Nagisa giggled again. "I would sure hope I know how to use it, it's been mine for the past nineteen years!"

Rei began to rub his eyes and turn around. "Alright, I must be dreaming. I must. That, or you put on quite a good show. Or this seawater is getting to me. Whatever it is, this is insane. Illogical." Rei shook his head. "It was nice meeting you, Nagisa." He started to walk away, still rubbing his eyes.

"Wait! Please."

Rei turned around. "Can't you get up and walk up here to talk?" There was a bit of distance between Nagisa and himself now, but Nagisa was still on the ground. His tail was still hitting the water, but his position had changed from on his side to now on his stomach, with his arms stretched in front of him. Nagisa's eyes showed just a bit of pain.

"What's your name?"

"Rei Ryugazaki," he said gently.

Nagisa's eyes lit up, but something about him showed a small sign of discomfort. "Will you be back tomorrow?"

Rei looked around him, and even pinched himself. The signs told him that it wasn't a dream, but that was the only logical answer. "Uh… If I can get to sleep, yes."

"Yay! I hope you can sleep, then, Rei-chan!" Nagisa quickly yelled, before waving good-bye and making his way towards the ocean.

Rei watched as Nagisa swam away, until he could no longer see the golden hair on his head.

Rei continued on home, and for the first time in a long time, he got a full night's sleep.