The character Kōseinen ("Good Young Man") is imprisoned in an isolated facility alongside three others: an elderly man and a cat. Identified by the codename "Pokerface" and designation N17, he is an ex-soldier with prior military service. During a sudden power outage that unlocks all cells, Kōseinen finds himself released only to discover the guards have vanished and the prison possesses no visible exits. Forced to collaborate with the other prisoners to solve the mystery of their confinement and escape, he observes the elderly prisoner exhibiting unusual behavior that suggests hidden knowledge about their circumstances. Kōseinen's specific connection to the other prisoners remains undefined.