High school student Yuuichi Katagiri holds dear his tight-knit group of friends, consisting of Yutori Kokorogi, Shiho Sawaragi, Makoto Shibe, and Tenji Mikasa. A theft of funds for an upcoming school trip leads to a rift, causing Shiho and Makoto, responsible for the money, to distance themselves. Subsequently, Yuuichi and his friends are lured into a meeting and rendered unconscious by unknown attackers. Upon regaining consciousness, they discover themselves trapped in a blank space with enigmatic individual Manabu-kun, who discloses that one among them has orchestrated the gathering to settle a personal debt of twenty million yen. To repay this debt, they must engage in a series of mental challenges that will scrutinize the essence of their bonds and humanity. Amid distress and seclusion, Yuuichi and his comrades must collaborate to navigate the trials. Yet, as buried emotions and troubled histories come to light, their seemingly solid friendship teeters on the brink of collapse.