Eiya Arakawa, a resolute young woman, arranges a meeting with Yuuga Oota, her best friend's former boyfriend, to learn why he left her for another man. At a café, Yuuga agrees to explain everything if Eiya can decipher the relationship dynamics of a nearby couple, which she does without difficulty. Impressed by her sharp perception and insight, Yuuga invites her to a private session where he reveals the Slave Control Method (SCM), a device that can enslave people. When SCM users duel, their minds are heavily influenced, and the loser is compelled to obey the winner after the duel ends due to heightened feelings of obligation. To test his abilities, Yuuga asks Eiya to act as a backup plan should he fall under someone else's control. He provides her with ten million yen to negotiate his freedom if needed. Though hesitant at first, Eiya accepts after recognizing a shared desire for a more fulfilling life. However, as a secret group rapidly acquires more slaves, Eiya becomes caught in a dangerous situation far beyond what she initially expected.