High school student Yuuichi Katagiri values his tight-knit group of friends, consisting of four classmates: Yutori Kokorogi, Shiho Sawaragi, Makoto Shibe, and Tenji Mikasa. However, when the money for the upcoming school trip is stolen, the incident causes Shiho and Makoto—who had been responsible for collecting the funds—to distance themselves from the rest of their class. Shortly thereafter, Yuuichi and his friends are tricked into meeting and knocked unconscious by unknown attackers. Upon waking, the group finds themselves locked in a white room with the controversial figure Manabu-kun, who reveals that one of the five has gathered them to settle a personal debt of twenty million yen. To repay this amount, they must take part in various psychological games that will test the true nature of their friendship and humanity. Distressed and cut off from the outside world, Yuuichi and his friends must cooperate to complete the games. But as their hidden feelings and troubled pasts begin to emerge, their seemingly unbreakable bond may soon shatter into irreparable pieces.