Through the use of a discreet mouthpiece called an SCM, anybody can turn a person into their slave through defeating them in a game. The only way for the slave to be freed is for their master to release them. Eia, a young woman described as cold and distant by her peers, first meets Yuuga Ohta when he breaks up with her best friend. The two instantly form a connection, and Yuuga, who wishes to participate in high stakes battles with other SCM users, confides in Eia, asking her to be his partner and to promise to defeat his captor if he is ever enslaved while participating in these dangerous games. Although Yuuga could see a part of Eia that nobody else could, she would soon come to regret meeting him with all of her heart.