On Christmas morning, Ryoko Fujino discovers the corpse of her classmate Takuya Kashiwagi in a snow-covered schoolyard. While police and high school conclude that he has committed suicide, Ryoko receives an anonymous letter accusing her of "murder by her classmate Shunji Oide and others." The media and SNS users who start making noise over suicide or homicide, or falling death. Principal Masao Tsuzaki tries to resolve the situation, but further accidents occur. Mysterious events that occur one after another. Ryoko, who is not convinced by the adult's response, stands up with a mysterious other school student, Kazuhiko Kanbara. "Why don't you try it? With us." An unprecedented school trial begins.