Oneechan Gokko

In the distant future, the mountain village of Kagami has been left behind by the extraordinary scientific progress reshaping the cities. Its residents still repeat an old warning: "If you misbehave, your Double will come." Akane Higure pays little attention to the legend, because she is too busy awaiting the return of her older sister Sui after an entire year in the hospital.

Sui finally comes home, but Akane's happiness does not last. Soon afterward, an anonymous phone call delivers one terrifying message: the girl in the house is not her sister. Caught between modern technology and the village's folklore about doubles, Akane is forced to doubt the face she knows best and discover what has returned home wearing Sui's identity.