The day started like any other at Hyosan High School. Students filled the hallways, laughter echoed off the lockers, and quiet dramas unfolded between friends and crushes. Lee Cheong-san, an average boy with a loyal heart, watched Nam On-jo from across the courtyard. She was his neighbor, his oldest friend, and the one person he could never seem to confess to. On-jo, cheerful and smart, was preoccupied with getting through the day, unaware of Cheong-san's feelings.
But far below the routine of the school, in the science lab, something unnatural had already begun.
Mr. Lee, a biology teacher haunted by his son's bullying and weakness, had created a virus—meant to strengthen the vulnerable by triggering intense survival instincts. But his experiment had gone terribly wrong. When a rat he tested it on became uncontrollably violent, he should have destroyed it. Instead, he locked it in a cage. One unfortunate student, curious and unwitting, approached that cage. The bite she received marked the beginning of the end.
Within hours, she collapsed in class. The school nurse rushed her to the infirmary, but something in the girl changed—her eyes glazed, her limbs twitched unnaturally, and her body convulsed until she stood up again. Not as herself, but as something hungry, something that attacked the nurse without hesitation.
The infection spread with terrifying speed. Students bitten turned into bloodthirsty monsters within minutes. Screams pierced the halls. Doors slammed. The virus didn't just spread—it devoured.
Cheong-san and On-jo found themselves caught in the chaos along with a handful of classmates: class president Nam-ra, quiet and logical; Lee Su-hyeok, a reformed delinquent with feelings for Nam-ra; and a mix of friends, outcasts, and rivals. They barricaded themselves in a classroom on the third floor, trembling as fists pounded on the doors from both sides—zombies outside and terrified students trying to get in.
Phones lost signal. The police didn't answer. The outside world didn't believe what was happening—yet.
As the group tried to survive, they faced more than just monsters. They had to make impossible choices: who to trust, who to help, and who to leave behind. One infected friend begged not to be killed. Another hid a bite. Paranoia grew. Even the living became dangerous.
And outside, the army was starting to notice. But for the students trapped inside, rescue felt like a fairy tale. The only thing that mattered now was making it to the next hour alive.