They wake up in a white room remembering nothing. The protagonist Takatou Keisuke and 6 others are locked up in these hidden white rooms. His childhood friend Hokari Kanae, classmate Andou Miyako, underclassmate Makiba Rika, English teacher Aoi Natsuki, same year Byakuya Rinne, and classmate Manaka Nemu. While still confused about their unusual situation, a "mystery voice" suddenly speaks to them: "A game has now started." In order to escape the room, Keisuke is the "unlocker" and one heroine the "keyhole". With an assigned act, he must "use the key".