The doujin is 3 parts. I am looking for part 2.
The main character is a copy of Nikumi from Food wars(but not her). She is married to this guy who is a failed musician. A foreign exchanged student(bbc) moves into the apartment from them.
They are really struggling with income so the guy and her make a deal that she will give him blow jobs for money. Later the good for nothing husband of hers steals her saved money and she runs away. The black dude consoles her and takes her to his room where they do it.