Kaneda, a young man, suffers trauma-induced amnesia after finding the body of his classmate and friend, Hiwako Shima. Following his release from the hospital by a mysterious benefactor, he returns to school and attempts to reconstruct his memories of the incident. Complicating matters further, his repressed memories have taken the form of a surreal entity with a head shaped like a crescent moon. Together, they embark on a quest to solve the mystery of Hiwako's murder.