Uchida Mayu is a high school student in a peaceful town near Tokyo. She suffers from violence from her stepfather and plans to run away to her uncle's home in Tokyo. As she is about to board the last bus to Tokyo, a terrible looking old person causes her to miss the bus. She attempts to walk across a ridge. Meanwhile, Mayu's uncle Uchida Kazuki is a freelancer writer. He chases after the hideous monster Yoshie who attacks people. Kazuki receives a phone call that his niece Mayu ran away. He begins a search for her and finds her cellphone on a mountain path. He sees Yoshie's picture on her cellphone.