Jûzô Murasaki is a boy miscast in his classroom, being frequently abused, tortured, beaten and humiliated by the bully Tôru Akai and his gang of juvenile punks. After years of repression, rejection and fear without facing Akai, he develops a psychopathic dual personality with a violent alter-ego. While living in the apartment 13 of a tenement building, he becomes unable to control his violent dark personality, who plots an evil revenge against his upper floor neighbor Akai and his family.