"If no one remembers it, does that mean it never happened?" The Rogetsu Kagura is a festival held once every ten years on Rogetsu Island in southern Japan. During the festival, five girls mysteriously disappeared. The girls were rescued by a detective, but all their memories were lost.

One of the girls who mysteriously disappeared, Ruka Mizunaki, had a faint memory of a melody:

• Girls playing instruments surrounded by masked figures
• A masked woman dancing in the moonlight as if possessed

The melody repeats and accelerates... and then the memory abruptly ends. What happened that day... Ruka has lived with this thought in her mind ever since.

Ten years later, two of the girls who mysteriously disappeared were killed one after the other. They were found with their faces covered, in a tragic state.

Determined to solve the mystery of their friends' deaths, the remaining girls, Misaki and Madoka, agree to travel to Rogetsu Island. Ruka decides to follow them to the island. Will they discover what lies beyond their lost memories?