Backstage Kimi no Iinari.

Masataka, an audio technician, has known Kei since his amateur rock days and used to treat him to ramen. But, now that Kei has become a top-selling artist, their positions are reversed. One day, Masataka is assigned to help with Kei's upcoming performance, and after the show he's invited to the after-party. Little did he realize it was an orgy!
(Source: Renta!)