Eiya Arakawa, eager to learn why her best friend's boyfriend deserted her for a man, requests a meeting with them. Yuuga Oota agrees to answer Eiya's questions only if she can properly identify the connection of a couple seated across from them, which she accomplishes on her first try. He brings her to a secret meeting, where he introduces her to the notion of Slave Control Method, or SCM, a retainer-like device that has the capacity to transform individuals into slaves. When two SCM users engage in a duel, the gadgets have a strong affect on their minds. Following the conclusion of the combat, the SCM heightens the loser's sense of obligation and forces them to bend to the will of the winner.