Hikari Kisaki lives day to day as an undercover investigator alongside her husband, hunting down the dark secrets of a criminal organization. Today, she infiltrates a casino used as a front by the group, posing as a guest to make contact with high-ranking member Takeda. Beside her, her husband, disguised as a waiter, carefully monitors the surroundings. As the game begins, Takeda gradually approaches Hikari. He proposes a high-stakes one-night showdown, and Hikari plans to intentionally lose in order to extract information—but her scheme is exposed. Her identity as an undercover agent is revealed, plunging her into a new and dangerous crisis.