Eimi, who came to Tokyo after graduating from junior high school, invites her sister Yu, who lives in her hometown of Shiga, to move to Tokyo with her. She is reluctant at first, but suddenly accepts and soon after goes missing. One day Eimi meets Hiyori, whose sister is also missing. Everything changes when the police contact her to inform her that they have found the body of a young woman in Lake Biwa, but the body is that of Hiyori's sister, not Yu. Together Eimi and Hiyori search for the murderer, but things take an unexpected turn.