The story follows protagonist , who awakens in a sterile white room with a mysterious collar around his neck. He discovers six women he knows from his school also trapped in the facility: Kanae Hokari : His childhood friend. Miyako Andou : The class president. Rika Makiba : An underclassman. Natsuki Aoi : His English teacher. Byakuya Rinne : A mysterious, aloof student.