Keisuke Takatou awakens in a featureless white room, with no memory of how or when he got there. As he tries to figure out where he is, he sees six girls he knows huddled around a large monitor: his childhood friend Kanae Hokari, class president Miyakou Ando, English teacher Natsuki Aoi, junior Rika Makiba, and classmates Rinne Byakuya and Nemu Manaka. As they try to understand their situation, a voice suddenly speaks through the monitor, saying, "The game will now begin." The rules are simple but brutal. Keisuke is assigned the role of "unlocker" and must choose one of the girls as his "keyhole," violating her in a specific way. Only after he completes this for five rounds will the group be promised freedom to leave. Miyakou refuses to accept the situation and vehemently denies participating. Suddenly, the room goes dark. When the lights return, Miyakou is strapped to an electric chair. "Withdrawal from the game will result in death," the mysterious voice announces, as the chair electrocutes her to death. With no other choice, the terrified captives agree, and the sadistic game begins, designed to awaken their carnal desires through pain—and pleasure.