Aki, a high school student, is at a family restaurant after school with her best friend Taki. Taki tells Aki about the dream she had last night about being attacked by "Hitotsume." Taki finishes talking about her dream and leaves, saying "I'm going to the drink bar," but she never came back--. Aki wanders around Tokyo in search of Taki, who has suddenly disappeared. At the same time, many people in Tokyo start to say they have seen "Hitotsume" in their dreams. Aki also gradually wanders into a strange world created by the mysterious "Hitotsume." She is guided by Taki's voice to the fictional city of Shibuya, where she can't tell if it's a dream or reality. What does she encounter there?