Kanojo wa Dare to demo Sex Suru 2

Based on the erotic game by Orcsoft.

Kazuhiro confesses his love to Erika, who then let's him watch her being banged by the PE teacher. Turns out the quiet and plain looking Erika is a rather penis hungry girl whose favourite pastime is sex with random guys. While shocked at the revelation, Kazuhiro still agrees to Erika's offer to record her sexual escapades on camera.