Sasaki Rena and Minemori Kotoha visit a woman named Takahashi Rika. Rika's brother married Sawayanagi Nana and died eight days later under suspicious circumstances. The doubtful Rika hired the Abiru Detective Agency to investigate the matter. Rika shows Rena the investigative report written on Sawayagani. In it she finds a copy of her high school yearbook, which contains a photo of Sawayanagi. Kotoha uses the photo to find some of Sawayanagi's old friends, but none of her former classmates remember her.