Ore to Anta no Aishou wa

Chancing upon a downcast salaryman in the park, college student Hikaru Hamada picks him up since he's his type. Though straight, the man has an interest in men, so Hikaru tries to embrace him. Yet the tables turn on Hikaru when the man enraptures him with his superior tongue technique. Though Hikaru is no bottom, he can't seem to refuse him. It's not the encounter they had expected, yet their meeting appears to have been fate...

(Source: Houbunsha, translated)