The world has collapsed due to a zombie pandemic. The protagonist, Mikoto Amano, wakes up in an unfamiliar place with no memory and is taken in by six girls. However, a shocking incident occurs: a man who was taken in alongside Mikoto is murdered, and the culprit is one of them. Set in the Tokyu Kabukicho Tower, mysteries and secrets unfold one after another within the now-sealed building. Will the girls, who have begun to form a bond, be able to uncover the truth behind the incident?