High school student Kai Ichihara receives an eerie email inviting him to play "Slave Go," a mobile game that can enslave certain individuals through capturing their picture. After unknowingly causing two people to vanish, Kai realizes the game is not a mere joke but a dangerous reality. His worst fears are confirmed when his close friend Rinna Date goes missing too.
Kai is soon approached by a mysterious man named William Gotou, who takes him to a room where enslaved captives partake in a life-threatening battle. This is all created by wealthy members of an underground community called "Society." People bet on the game using a currency called Delos, and losing all one's money results in being captured as a slave.
Kai wins his first game but only to discover that Rinna is now a slave as well. To set her free, he must pay an exorbitant fee of one hundred million Delos. With William's assistance, Kai embarks on a mission to capture powerful slaves, expecting to set both Rinna and himself free from the clutches of Society's pernicious game.
