Younger sister Mayu and older brother Kenji attend the same school. The two of them secretly had a physical relationship. But her sister was a so-called 'tsundere' who behaved strangely to her brother outside. One day, Kenji hears rumors that Mayu has a boyfriend in the same class. Kenji couldn't hold back with jealousy, took Mayu around, and had unfaithful vaginal cum shot sex everywhere in the school.
