Vastness Kuukyo no Ikenie-tachi

Vastness consists of three mini-stories unrelated to each other. The first follows the sexual escapades of a female student who seduces her schoolmates; the second mainly focuses on a treatment of a particular kind received by a man from a female doctor and nurse in a hospital; the third tells the story of a young girl who discovers her sexuality and eventually gets married.

[From Mobygames]