Hanako Kasato is a bright student at Hachistu High, just a few months away from graduating from junior year when a tragedy strikes and a woman is killed in her own home. As the crimes continue, she faces a grim reality that the killer might be the same one who killed her mother seven years ago. The young student decides to volunteer, helping with the investigation alongside her uncle and Hisato Nakami, a first-year senior, to recall the events following her mother's death. Will she be able to recover her memories before it's too late? Or will she be the last victim of the perpetrator?