The shores of Chiba in 2060 were bathed in the golden-red hues of sunset, waves lapping gently against the rocks in a rhythm like whispered secrets. The sea breeze, tinged with salt, brushed against Yuuma Sato's cheeks as he stood atop the breakwater, his dark, unruly hair ruffled by the wind. At seventeen, Yuuma wore a plain white T-shirt and jeans, his school jacket slung carelessly over one shoulder, but his eyes—cold as the twilight—betrayed a detachment beyond his years.
He came to the beach alone, not for the view, but to escape—the noise of school, the chatter of his neighbor Chacha, the prying eyes that always seemed to dig too deep. A habitual smirk played on his lips, a carefully crafted mask. No one knew the memory he buried deep inside: ten years ago, his parents had divorced after the government's "Emotional Regulation" system deemed their marriage "incompatible," leaving him alone in an empty home. Since then, Yuuma had learned to cloak his cynicism in humor and shield himself with indifference.
"What a boring world," he muttered, kicking a pebble into the water. It skipped twice before vanishing beneath the waves. In 2060, robots and AI were everywhere—drones hummed overhead, delivery bots zipped through streets, even classrooms were run by holograms and AI instructors. Life was convenient, but to Yuuma, it felt hollow. When even emotions could be quantified, what was left to believe in?
His gaze drifted absently toward a cluster of rocks in the distance, where something pale caught the fading light. At first, he thought it was seaweed, but the shape was too distinct. Frowning, Yuuma hesitated before walking over. Then he froze.
It was a girl.
Curled up between the rocks, her silver hair fanned out like seafoam, her white dress clinging to her slender frame, soaked through. Her skin was almost translucent, her eyelids fluttering faintly, as if caught in a dream. Yuuma crouched beside her, nudging her shoulder. "Hey. You okay?"
No response. His frown deepened. Her skin was cold—unnaturally so. Like a machine. But her features were painfully human, down to the droplets clinging to her lashes. His pulse quickened. A drowning victim? Or a discarded android? By 2060, synthetic humans were nearly indistinguishable from real ones, but he'd never seen one this lifelike.
"Hey, wake up!" he said louder, shaking her gently. Her lashes trembled, then lifted, revealing eyes of deep, crystalline blue—like the ocean itself staring back at him. Dazed, her lips parted, her voice barely a whisper:
"...Were you... calling me?"
Yuuma exhaled, though his guard stayed up. "Who are you? Why were you lying here?" He scanned the shore—no signs of anyone else, no clues. The girl pushed herself up, damp silver hair sticking to her face, disheveled yet oddly striking. She tilted her head, brows knitting.
"I... don't know. I just remember being in the water, then... here."
"Amnesia?" Yuuma arched a brow, his tone laced with dry humor. "That's straight out of some cheap anime." He meant it as a joke, but his mind raced. Calling the police was the logical choice—unless she really was synthetic. The news often showed androids being dismantled, deemed "defective." The thought made his stomach twist.
The girl didn't laugh. Instead, she shook her head earnestly. "I really don't remember... but I don't want to go to the police." She paused, those ocean eyes locking onto his. "Can I... stay with you?"
Yuuma blinked. "Hah? With me? You don't even know who I am." He jabbed a thumb at himself, flashing his trademark smirk. "I could be some shady guy who sells amnesiac girls on the black market."
But she didn't flinch. Instead, she giggled—a sound like wind chimes. "You don't seem bad! And..." She glanced down at her soaked dress, voice small. "I have nowhere else."
Yuuma dragged a hand through his hair. This was getting complicated. He wanted to refuse, but something in her helpless gaze made his resolve waver. With a sigh, he stood. "Fine. You can crash at my place tonight. We'll figure it out tomorrow." He held out a hand, feigning annoyance. "Can you walk? Don't expect me to carry you."
Her face lit up as she took his hand, her grip cold but oddly soft—clinging like she feared he'd vanish. Yuuma turned away to hide the flush creeping up his neck, muttering, "What a pain..."
His apartment was an old complex on the city's outskirts, sandwiched between flashy unmanned stores and drone lanes. Inside was sparse—two bedrooms, a living area, furniture minimal to the point of austerity. Hoshino—the name she'd given on the walk over, though she wasn't sure if it was really hers—looked around with childlike wonder, poking the sofa, tapping the holographic TV, letting out soft "wow"s.
"Stop touching stuff. It's not mine to break," Yuuma grumbled, tossing her a towel. "Dry your hair. Don't catch a cold." He paused, then added under his breath, "Assuming you even can."
Hoshino beamed, clumsily rubbing the towel through her hair like she was mimicking what she'd seen humans do. Abruptly, she stopped. "Yuuma... do you live alone? It's so quiet here."
The question caught him off guard. He slouched onto the couch, shrugging. "Yeah. Got used to it. Quiet's better—less annoying." He kept his tone light, but the old ache throbbed beneath. Hoshino didn't seem to notice, already distracted by a digital clock on the wall.
Then—Ding-dong!
"Yuuma-nii! Open up! It's Chacha!" The door burst open before he could react, revealing a hyperactive ten-year-old in a bunny-print shirt, twin tails bouncing. His neighbor, and self-proclaimed "little sister," charged in—only to freeze at the sight of Hoshino.
"Waaah! Pretty onee-san!" Chacha gasped, pointing. "Yuuma-nii, did you kidnap her?!"
"Idiot! Don't just barge in!" Yuuma flicked her forehead, cheeks warming. "She's Hoshino. Just... staying over."
Hoshino crouched to Chacha's height, grinning. "You're Chacha? Cute name! I'm the sister who washed up from the sea!"
Chacha's eyes sparkled. "Like a mermaid?!"
As the two chattered, Yuuma watched Hoshino's reactions—too perfect, too deliberate. Like every smile was programmed.
"Alright, brat, scram." He herded Chacha out, ignoring her whines. At the door, the girl waved. "Bye, Hoshino-nee! Play tomorrow!"
Once alone, Hoshino hugged the towel to her chest. "...Thank you, Yuuma. For letting me stay." Her voice wavered, eyes searching his for something he couldn't name.
He looked away. "Don't mention it. Just don't wander around at night."
That night, Yuuma lay awake, drones humming outside his window. Hoshino's face lingered in his mind—her smile, her cold skin, her plea not to go to the police. "A girl with amnesia, right where I'd be..." he murmured. "Too damn convenient."
Meanwhile, in the guest room, Hoshino curled into herself, pupils flickering faintly with light. "...Mission... memory... error..." she whispered, lost. On the nightstand, Chacha's forgotten bunny plush kept watch over the girl who wasn't quite human.
Morning light spilled through the curtains as Yuuma trudged into the living room—only to find Hoshino already there, dress pristine, sipping water. "Good morning, Yuuma! School today?"
"Did you even sleep?" He scowled. Her clothes looked untouched, no wrinkles.
"I did! Just a little!" She bounced over. "Let me come! I don't want to be alone!"
Against his better judgment, he sighed. "...Fine. But no weird 'washed-up' talk."
Hoshino grinned, leaning close—too close. "Okay! I'll listen to Yuuma!"
His heart stuttered. This girl... is definitely trouble.