Kirei na Oniisan ga Ore no Pet ni Narimashita

Haruki is a prep student who is living alone with no parents nor money. He currently works as a cabaret boy. One night, he met a beautiful drunkard older mister who was sleeping in the garbage area. Thus, Haruki decided to take him home as the thought of leaving him alone was too dangerous. However, the mister suddenly attacked him as he mistook the situation for a one-night stand and made him cum dry. Haruki continues living with this mysterious mister because the sex-service felt so good that he could melt.

(Source: Kaiohsha, translated)