Dosukebe neesan: Hamegurui(1994)

Natsumi, a female college student attending a university in Tokyo, lives in a luxury apartment left to her by her parents and leads a carefree life. However, her older sister Keiko moves into Natsumi's room after her brother-in-law dies in an accident. Natsumi, who is quite promiscuous, is no longer able to have the sex she loves because of her sister...