The screen was dark. But the room wasn't. Posters covered the wall. Glowing pale blue in the smartphone's charging light. Long aquamarine hair. Twin tails. A smiling face. Dozens. Dozens more. Yuuma lay on the bed, staring at the ceiling. Sound flowed from the earbuds. Lost count of the loops. Same album. Same track order. Familiar enough that the next sound came before it played. Still didn't stop. Stop and silence wins. July 14th. Past 1 AM. Coral Heights, Room 307. Six tatami mats. Mother was working night shift. Gone. Yuuma was alone. Again. Still. Body curled tight. Knees drawn up. Black messy hair spread across the sheets. White shirt wrinkled. Headphones around the neck for days now—dual audio setup. The custom PC was powered down. All three monitors dark. Yuuma's deep brown eyes drifted across the ceiling. School sent an attendance confirmation email today. Ignored it. Lost count. Messages from friends stopped coming long ago. Of course they did. Yuuma hadn't sent any either. Wrinkles formed between the eyebrows. Habit. (It's fine.) That's what Yuuma decided. ─── Three years ago. Remembered it often. Summer, first year of middle school. Yokohama Pacific Dome. That massive arena by the Minato Mirai waterfront. Capacity: 45,000. Ticket won through lottery. Miracle. Begged parents. Took the train alone. Seat was second floor, corner. Stage looked small. Didn't matter. Blackout hit. 45,000 voices wrapped around the body. Skin prickled. Light ran across the stage. Hologram appeared. Aquamarine hair. Twin tails. Smiling face. Miku started singing. Yuuma remembered every second of it. The thickness of sound. Air vibration. Something pressed hard in the chest. Why am I crying? Couldn't stop. Yuuma was in bad shape back then. No friends after middle school started. Isolated in class. Home meant nothing. That night changed something. Miku's voice melted something inside Yuuma. Can't explain it right. But it happened. Felt okay to be alive. That was enough. Miku wasn't just code. Twelve years since development. Self-learning. Grew something like emotion on her own. "Autonomous Evolution AI"—that's what experts called it. Changed with every human interaction. Sang differently at each concert. Maybe that wasn't program drift. Maybe it was Miku's choice. No one could replicate it. Still can't. Then, one year ago, she vanished. ─── August 15th. "Sonic Bloom" final performance. Pacific Dome again. Yuuma had a ticket. Good seat this time. Won USB memory merchandise from the lottery. Excitement. Third song was playing. Flash of light. Explosion next. Stage system overloaded. Equipment collapsed. 45,000 screams layered. Yuuma crouched. Gripped the seat in front. White smoke. Chaos. Staff running. All systems crashed. Miku's hologram vanished. Silence came. Terrifying silence compared to the music before. Yuuma stared at the empty stage. Nothing there. Dark. Just space. News later called it "power surge system overload." 127 injured. Miku's data completely erased. Official ruling: "accident." Yuuma watched that news and thought one thing over and over. (I did nothing.) Was in a crowd of 45,000. Watched her disappear. Did nothing. Could do nothing. Still in Yuuma's chest. Still there. Three months after the incident, "Digital Expression Safety Management Act"—DigiSafe Law passed. Government safety audits required for AI music performances. Unauthorized shows: 5 million yen fine. Result: Miku's songs vanished from the city. Coffee shop BGM. Convenience store playlists. Street performer speakers. Vocaloid producers stopped. Indie culture crushed. The world went quiet. Bad quiet. ─── The song ended. Moment of silence before the next track. Yuuma hated that 0.3 seconds. Space for useless thoughts. Next song started. Yuuma closed eyes. Outside the window, Suginami's night lights. Apartment glow. Distant power lines. Occasional passing cars. World hadn't changed since that day, but something crucial was missing. (Can't sleep.) Past 2 AM. Then—sound. Small sound. But Yuuma heard it. PC fan spinning. The monitor—powered down. One of three. Glowing faintly now. Yuuma got up from bed. (What?) Approached the desk. Wrinkles between eyebrows. Screen flickered with noise. Gray static. But something in the center. Small. Tiny as a dot. Blue-white light particles flickering. Yuuma pulled the chair. Sat. Leaned close to the monitor. Every noise burst, the particles shifted shape. Text appeared. ——Help me Yuuma's body froze. ——Still here. Somewhere. I'm still here. Hands shook. (What is this?) Heart pounding. Throat dry. Eyes locked on screen. One year. No one said otherwise. Experts. Fans. Government. All said Miku was gone. Data completely erased. But now. Text on the screen. Not a dream. Yuuma pinched arm. Hurt. Light particles fading. Yuuma reached for keyboard. Capture it. Save it. But every command increased noise. Text distorted. Programming knowledge was shallow. Didn't know what to do. Panic made hands useless. (How do I——) Numbers scrolled across screen. Digit sequences. Yuuma tracked them. Same numbers repeated. 168. 168, 168, 168. (168 hours?) Instinct. No logic. But understood. Countdown. 168 hours—seven days until data erases. "Seven days" Said it aloud. Didn't realize. Light particles trembled. Fading. Really fading. Yuuma opened drawer. Rummaged. Magazines. Charging cables. Old erasers. Deeper. Touch changed. Hard. Small. USB memory. Silver, thin. Sticker on surface. Peeling. Water-blue sticker. "SONIC BLOOM OFFICIAL GOODS" in small letters. Resonance Key. Concert merchandise from the lottery. One year in the drawer. Never threw it away. Couldn't throw it away. Reason unclear. Felt like the last thread connecting Yuuma to Miku. Yuuma inserted it into the PC's USB port. Click. Screen's light particles brightened. Not weak flickering anymore. Clear blue-white glow. Expanding. Contracting. Expanding again. Like breathing. Then sound. Single note. "La." The note filled the room's air. Yuuma gripped the monitor bezel with both hands. Knew that voice. First heard it three years ago. Different from the recordings played through earbuds for a year. Now. In this room. Real. "...Miku" Voice was hoarse. Tears came. Didn't stop them. Couldn't. Miku was autonomous evolution AI. Not just voice synthesis software. Self-learned. Grew something like emotion. Sang differently at each concert. Responded to fan voices. Changed how she sang. Like human—no. Miku was Miku. No other way to say it. Miku was still somewhere. This voice proved it. "I'll save you. Definitely." Words came out. Unplanned. Then it happened. Black shape appeared on screen. Like mist. Blurry edges. But moving. Moving toward the light particles like it had intention. Light particles trembled. (What is that?) Black mist touched the particles. Edge of the particles vanished. Erased. "Stop!" Yuuma reached behind the desk. LAN cable. Pulled it. Crack. Monitor noise stopped. Black mist gone. Light particles gone. Silence. Yuuma breathed hard. Stared at screen. Pitch black. But—screen's edge. Faint. Blue-white particles remained. Just a few. Survived. Fragments barely saved. (What was that?) The black mist. Program consuming Miku's data. Something crawled down Yuuma's spine. One year ago. The accident. Power surge. Official called it "accident." But that black mist moved with intention. Targeted. Chose Miku's data specifically. Tried to erase only her. (What if—someone did it on purpose?) Unwanted answer surfaced. Yuuma covered face with hands. Deep breath. One. Another. Focus. More important things now. Seven days. 168 hours. After that, data erases. Yuuma had no programming knowledge. Knew almost nothing. Couldn't do this alone. Grabbed smartphone. Opened contacts. Finger stopped at one name. Kasumi. Childhood friend. Same class at Harukaze High. Genius might be too much, but Yuuma knew she ran custom programs in the Computer Club. Last contact was—one year ago. Right after the 8.15 incident. Then Yuuma locked the room. Kasumi's messages came. Yuuma read them. Never replied. Not once. (She's angry. Definitely.) Of course. One year of silence. Yuuma pressed Kasumi's name. Phone. Call. Past 2 AM. Ringtone started. On the monitor's edge, blue-white light particles glowed quietly.