When the protagonists were children they visited the isolated island of "Rōgetsu Island." In the midst of a festival, they disappeared mysteriously. The title begins when the girls decide to go back and visit the island again in search of the lost memories of that day.
Attempt to repel encroaching ghosts, relying only on a faint glow from a flashlight and a camera with the ability to photograph unimaginable things, the Camera Obscura.