Three Naked Sisters: Lustful Intercourse: The youngest sister Miyo is an illustrator but she is a shut-in. She does not socialize with anybody. The middle sister Mizuki is working at a bar. She gives all of the money she earns to her boyfriend, who is actually married. One day, the oldest sister Hoshimi, who is a painter, returns home. Hoshimi brings different men to the house, and has sex with them. The two younger sisters are thrown off by her behavior, until they find the reason for Hoshimi's frustration.