During the last summer vacation of their high school lives, Akira Takizawa, Michio Oshima, and Osamu Kobayashi, who still haven't decided on their future careers, gather in a classroom to take supplementary lessons. Natsuko Izumi appears there, who has just been assigned to the new position due to the homeroom teacher being on maternity leave. Natsuko, who coolly and dispassionately serves as the substitute teacher, has a past in which she had to keep her distance from her students. Meanwhile, Akira was forced to repeat the year after committing a violent act to save his classmate Shiho Matsuyama from being raped by the head teacher Yamashita. One day, Yamashita accidentally finds out about Natsuko's past, and he threatens her, relentlessly playing with and abusing her. Having caught a glimpse of their relationship, Akira is confused but is drawn to Natsuko. Shiho is also heartbroken by her feelings for Akira. However, Yamashita's plan is carried out once again...