Set in Japan predominantly during the late 1990s, the series chronicles the life of Ryōgi clan heiress, Shiki Ryōgi, and her relationship with fellow classmate Mikiya Kokutō. Both the light novel and the films are depicted in anachronical order with each chapter/film serving as part of one collective narrative. The series deals with the paranormal and tackles mature themes such as suicide, rape, parricide, incest and murder. Its lore and story draws inspiration from various religious philosophies and psychological concepts such as multiple personalities; the anima and animus; the nature of sin; life, death and reincarnation; and the paradoxical nature of the Taiji.