A weary office lady plagued by bad luck dies and reincarnates into the world of an otome game set in Japan's Taisho era. She awakens as Ruri, a notorious villainess whose fate is to be killed by Haku, the overpowered and deranged boss of a Chinese mafia syndicate. To escape this grim destiny, Ruri decides to gamble everything on a risky bet she is certain will catch the attention of Haku, a man who lives only for danger and stimulation. The plan works too well. Haku, who has never wanted anything in his life, becomes obsessively fixated on Ruri, declaring that her entire being belongs to him. The story follows their dangerous romantic relationship as Ruri navigates her villainess role in the game's plot while trying to manage the unpredictable and possessive mafia boss who now refuses to let her go.

The main characters are Ruri, a former office worker who uses her knowledge of the game's story to survive, and Haku, a powerful and thrill-seeking mafia leader whose boredom is conquered only by his sudden obsession with her. The setting is a fictionalized version of the Taisho period, blending historical aesthetics with the otome game framework of a villainess facing a bad ending.

The central narrative arc follows Ruri’s initial desperate gamble to survive, which triggers Haku’s possessive pursuit. This leads to a major story arc focused on the dangerous romance between a villainess marked for death and the mafia boss who claims her as his own, forcing both characters to change as their high-stakes relationship develops. The complete story is told over three volumes.