Himitsu wa Sarashite Mederubeki

Tokumoto, who's hardworking and highly trusted by people around, has a secret. That is, he uses sex toys to play with his behind. As he's a virgin in his 30s, his butt is prepped but it wasn't used at all. He also thinks it's bothersome to find a lover. One day, Tokumoto was hunting for sex toys when he was seen by Kayama, a sociable, friendly junior man. However, Kayama, who has been interested in Tokumoto for some reason, suddenly asked, "Can't I be your partner?"

(Source: Kaiousha, translated)