Eager to understand why her best friend's boyfriend dumped her for a man, the headstrong Eiya Arakawa suggests meeting with them. At a café, Yuuga Oota agrees to answer Eiya's questions only if she can correctly determine the relationship of a couple sitting across from them, which she manages on her first try. Amazed by her remarkable intellect and intuition, he invites her to a private meeting where he introduces her to the concept of the Slave Control Method, or SCM, a retainer-like device capable of turning people into slaves. When two SCM users enter a duel, the devices exert a powerful influence on their brains. Once the duel ends, the SCM amplifies the loser's sense of obligation and forces them to submit to the winner's will. Desperately wanting to test his own abilities, Yuuga asks Eiya to act as his insurance in case he himself becomes a slave. Granted access to 10 million yen, Eiya's task is to convince Yuuga's would-be master to free him from servitude. Though hesitant at first, Yuuga's words resonate with her personal yearning for something more from life, and she agrees to his request. However, when a mysterious organization begins rapidly accumulating slaves, Eiya becomes entangled in a game far more dangerous than she ever could have imagined.