Mote Papa to Dakaretai Junjou Koushi summary:
I can't stop wanting you. After he discovers he is gay, university student Oda wants to have sex with someone, so he meets up with someone he finds on a dating website. That man is a gentleman, so Oda calls him "Casanova." They were supposed to have a one-night stand and not know each other's identities, but whatever he does, Oda cannot forget him...