Yumi, a veteran teacher, was trusted by parents and relied on by her superiors and colleagues. However, Yumi had a serious secret that betrayed their trust. She had entered into a physical relationship with her student, Okamoto. She had not told anyone at school or around her, and had been doing so with the utmost caution... Okamoto, still young and in the midst of puberty, was beginning to crave excitement. So, in search of new excitement, he started to play with Yumi's body during class...