Kainarasu Hazu ga, Aegasarete Komattemasu.

Akira Naito: Works at a design office. 29 years old. Work is tough. His subject of romantic interest: men. He has a policy - to never go to bed with the same person twice. After meeting the sexually inexperienced Seo at a bar, he begins giving him sex lessons to kill time. This straight man was meant to be his to ravish, but things aren't going as expected? A young, earnest ikemen and a beautiful man, romantically hurt in the past, engage in sex lessons on Friday nights.

(Source: Libre, translated)