Stale cigarette smoke and the clang of a steel door seals the world behind him. Juyeong sits on a cot inside a juvenile detention center, caged for the attempted murder of his father, Gang-ryong — a man whose shadow has crushed him long before he learned how to throw a punch. He clings to one lifeline: a future in Seoul with Dayeon, the childhood friend whose smile still cuts through the concrete walls of this place. The plan is survive, serve the time, and walk out to her waiting arms.

Then the news arrives. Dayeon is dead. A truck. A rogue accident, the report says, but the truth lands with the weight of an anvil: Gang-ryong was behind the wheel. The hope that kept Juyeong breathing evaporates, replaced by something black and cold. That is when his father regains consciousness and delivers his offer — not an apology, not a confession, but an ultimatum. "If you want revenge, become the king of this detention center." Juyeong looks past the bars at the hierarchy of violence that rules this concrete hell, at the gangs and the guards and the unspoken law that power is the only currency that spends. He did not choose this war. But the throne his father is pointing at is the only path to avenge her.

Also known as: Juvenile Detention Center, 소년교도소, Sonyeon Gyodoso, Boys' Prison.