Seventh grader Hayashi Renei is troubled by a strange dream: Her dead brother, who was killed in an automobile accident, comes back to life as Coo. The dream comes again the following night and then every night thereafter.

Coo's world is a cruel one–crueler than the real world, even–with its own share of pain, suffering, and sadness. Renei is searching for her house with her brother and others whom she meets in Coo's world so that she can return to reality and the land of the living…