Shinshi to Norainu

From Bakeneko Scanlations:

Banri is a college student who goes with the flow. One day, he meets a well educated business man, Masaomi, with whom he ends up in bed with. This relationship was supposed to be a one night stand, but Banri confesses that he wants to meet Masaomi again after discovering his cute and honest side.
However, Masaomi tells him that he has a fiancée and will never be meeting Banri again, he leaves by ending the night with those words. Few days later, Banri discovers that Masaomi is actually the heir of a big and well known plutocrat!? With the main story, follows the love story between a station attendant and a divorced business man and the bargaining love between a manager and his secretary.