A younger brother who went to college in the city decides to live with his older sister who has moved to Tokyo. However, his older sister is a total slut, and on weekends she has a blast with her slutty girlfriends talking about sex! When her younger brother is dragged into the circle and it is discovered that he is a virgin...they start a sex study session and experience deflowering! He doesn't want to lose his irreplaceable first experience like this! But he can't stop pistoning because of the pleasure of his first sex! In the end, all the sluts beg for his dick and he ejaculates all night long!