Kuchi no Naka ni Amaku Hurete

Four years after graduating, Shimazaki, who works as a hairdresser's assistant, has loved his friend, Tateyama, a haircut model and a fellow sweets lover, since high school.

When Tateyama starts working, he begs Shimazaki to be his roommate. His naturally sweet smile persuades him, and they end up sharing a room.

One night, when Shimazaki finds himself thinking, "I want to taste those lips that always speak sweet words to me," Tateyama touches him as if he can see through Shimazaki's hunger for love. The boundaries of their apartment collapse, and the two drown in sweet desire...

A love story about an unaware, obsessed, spoiled doggy and an uninhibited gay man who can't get rid of his feelings.

(I translated the original synopsis and wrote it in English, since the one on MangaUpdates has a part edited out)