Kara no Shoujo - Season 1

Private detective Reiji receives a peculiar request from a young woman, who asks him to locate her "true self." Concurrently, a string of bizarre murders begins, and he is also engaged to look into these cases. His younger sister attends Yukari Girls' High School, where two students have now disappeared. The school's vice principal, Tokio, hires Reiji to find them. Thus, the detective is presented with three separate assignments simultaneously. To gather information, he takes a position undercover at the school. There he encounters Toko, the same girl who earlier asked him to find her real identity. The murders continue unabated, creating a deepening spiral of tragedy. Within this grim situation, perhaps only a girl's smile can offer a path forward.