Tokumei no Kanojo-tachi

This manga follows the sexual adventures of middle management businessman Yamashita Takahiro. Yamashita is 32 years old and single, and he does not have a girlfriend. In fact, he has problems interacting with women normally. However, he makes a hobby of experiencing adult entertainment. He pays to sleep with many different women in different locations, talking with them as he is serviced in various ways.

(Source: MangaHelpers)