Akira Mitarai is a second-year employee at the central branch of Karasu Bank, one of Japan's most profitable banks. His gift for math lets him catch accounting mistakes at a glance, but it also leaves his daily work dull. His existence feels hollow until a sudden transfer derails everything. He is moved to the Appraisal Unit, and his new boss, Usami, leads him through a secret passage beneath the bank. There he learns the truth: the bank runs a vast underground casino, and his unit manages both the games and the gamblers. Players stake their lives as collateral, and at the highest level a loss means death. Amid the confusion, Mitarai meets Shin Mafutsu, a brilliant and enigmatic gambler who exposes his rivals' cheating and wins. Captivated, Mitarai chooses to step into this deadly world as Shin's bank representative. The result is a tense psychological thriller built on life-or-death gambling.