Minato's behaviour is increasingly worrying. His mother, Saki, is looking for the reasons at school. Here she encounters Hori, a teacher who she believes is the source of her son's problems. The teacher denies the accusations, but Saki refuses to listen. She becomes obsessed with proving Hori's guilt and starts to pursue him. As the story unfolds, we see the different perspectives of Saki, Hori and Minato, each with their own version of the truth. Will it be revealed which one of them is the real monster?