When Kaede's mother died, she left her a small box. Inside was a mirror — and Akeha, Kaede's exact double, lived inside it. Kaede is quiet and methodical; Akeha is impulsive and direct. When strange events begin at school, the two work together: Kaede visits crime scenes and interviews witnesses in the present, while Akeha can step into the past to gather information that no longer exists in the present.