Yasuko is an ordinary girl who often feels overshadowed by her younger sister, Ayaka, who deliberately antagonizes her. Yasuko begins to suspect something seriously wrong with Ayaka after their mother discloses that Ayaka's appearance drastically changed after her first year of life, and she notices several girls around town who look strikingly similar to Ayaka.
When a severely disfigured Ryo reaches out to Yasuko and reveals the truth about Tomie, Yasuko agrees to help him trap "Ayaka" and keep her contained. The two dedicate decades to guarding Tomie.
