After two years together, Shoko (An Sasakura), a fellow teacher, begins thinking seriously about marriage with her boyfriend Tadashi. However, he shows no signs of proposing, leaving her increasingly anxious. One day, a message from a former student, Aimi (Mikako Abe), arrives on Tadashi's phone. Shoko, noticing it by chance, decides to read the message. To her shock, it contains a blackmail threat along with a photo showing Tadashi touching the buttocks of another ex-student, Eri (Maeda Ako). Devastated by the contents, Shoko's emotions spiral into turmoil.