Airi decides to work as a tutor at the request of Seiji, the eldest son of the Sasaki family who lives next door, who cannot give up on his dream of going to college despite his father's opposition. That first day... Airi, who is waiting alone in her room for Seiji who hasn't come home from school, gets excited at the sight of a boy around her age, and ends up masturbating to help her with her frustration. What she doesn't know is that her father, Haruo, is watching her... After the incident, Airi's bra was missing from her room.