Seven days had passed since he left the hospital.
Classroom 2-A had become an anchor again. The smell of chalk dust, the rows of desks covered in carved initials, the ceiling fan's drone — these were the artificial gravity holding Yoon Jaeho's sanity in place. He stood at the front of the chalkboard. He wrote formulas. He graded assignments. He let routine swallow the physical trauma that medical science had failed to record.
The wireless headphones had become an extension of his anatomy. He wore them in the corridors, in the teachers' room, in the cafeteria. Running manufactured white noise at maximum volume to kill the leaking human frequencies around him.
Friday afternoon. The bus stop outside the school gates.
Bus number 41 pushed forward, exhaling a sharp hiss from its hydraulic brakes. Jaeho stepped up, tapped his transit card to the scanner, and pressed toward the rear area near the exit doors.
The metal box was packed tight. The air inside was sealed shut, trapping a suffocating mixture: the sour sweat of middle school uniforms, the sharp smell of green onion from a woman's grocery bag, and the residue of cheap tobacco clinging to the jacket of a middle-aged man asleep on his feet.
Jaeho leaned against the steel pole. His eyes followed the asphalt streaming past the clouded window. White noise filled his ears, muffling the world. Everything was normal. Safe. Tediously ordinary.
Then the sound broke through.
Not a single leaking tone. Not the lone scraping note he'd heard from Nurse Han's hospital room.
This was a chorus.
Jaeho's brow drew together. He pressed the volume-up button in his pocket. The sound didn't sink. It climbed, consuming the white noise inside his headphones.
He yanked the right earpiece away from his ear roughly.
The bus engine roared. Conversations murmured. Shoe soles scraped across the floor. All of it sounded ordinary. But beneath that layer of physical sound, dozens of human frequencies were resonating and striking his eardrums all at once.
And they were not sounding at different base tones.
They were singing in one identical pitch. Taut. High and thin. Uniform.
It was the sound of steel suspension wire being pulled forcibly past the limit of its elasticity. Vibrating in the final seconds before it snapped.
Jaeho's breath shortened. His head snapped around.
The woman with the grocery bags was typing on her phone screen. The man in the tobacco jacket was still snoring softly. Two female students in the seats ahead were laughing at something in one of their hands.
Nobody was clutching their chest. No pale faces. Their biology was operating perfectly.
But the high pitch in Jaeho's ears kept sharpening. Slicing through his auditory nerves. Merging into one massive resonance that shook his skull.
The thirty-six lives inside this metal box were not emitting different amounts of remaining time. The sound of wire about to snap was resonating from every single chest. Converging on the exact same coordinate.
This second.
*"Get down!"*
Jaeho's vocal cords tore the command out. His instinct detonated before his brain had finished assembling its logic.
Time slowed inside the bus.
The two students in front turned to look at him with furrowed brows. The woman yanked her child's shoulder hard, shifting her body away from Jaeho as though he had just expelled a lethal pathogen. The man in the jacket startled awake, clicking his tongue with irritation.
Someone in the middle rows murmured one word that carried perfectly through the sudden social silence.
*"Insane."*
Jaeho didn't meet any of their stares. His knees had already bent hard. He dropped himself to the dirty rubber-coated floor, tucking his head behind the fold of both arms.
One second of excruciating, awkward silence passed.
Then, without a flash of light. Without the sound of an explosion. Without any warning from the world outside.
The bus was cut open, along with everyone inside it, split clean in two along a horizontal line.