Boku no Kanojo ga Fuzaichuu ni, Kanojo no Shinyuu no AV Joyuu to Hamemakutta Hibi no Danpen

Hajime is a college student who's practically living with his girlfriend Rio, spending most nights at her place. One day, by accident, he finds out that Rio's best friend Yuri is actually the AV actress Yura Kanou. Excited by the thought that an AV actress is sleeping right next to him, Hajime is unable to hold back...

(Source: DMM, translated)

Note: Manga adaptation of a live-action JAV (SSNI-623).