A prequel to Meakashi-hen. Shion is sent away to the all-girls school, St. Lucia Academy, for confinement. One day, a male teacher's body was found in the school swimming pool and the first discoverer, Kosaka Mizuho, is summoned to the chairman's office to report the details. Shion hears rumors about how Mizuho's grandmother is after Mizuho's life and the girl is taking refuge in the school, so Shion approaches the aloof Mizuho.
NOTE: The story is divided into a total of eight chapters: four "Question" arcs and four "Answer" arcs. Each chapter keeps the same main characters, but ends in a different way. However, each chapter gives valuable answers, hints, and clues to the previous one, while at the same time bringing forth even more mysteries.
The question arcs are: Onikakushi-hen, Watanagashi-hen, Tatarigoroshi-hen and Himatsubushi-hen.
The answer arcs are: Meakashi-hen, Tsumihoroboshi-hen, Minagoroshi-hen and Matsuribayashi-hen.
The side story arcs are: Onisarashi-hen, Yoigoshi-hen, and Utsutsukowashi-hen
