From MangaHelpers:
Tonuno has a wife and a daughter, Kitsuka, but he also has a mistress. His wife has been acting colder towards him lately, and he is critical of the fact that she still hasn't lost all of the fat from having their daughter years earlier. He meets his lover Moemi regularly, for sex and companionship, and he believes he has successfully kept it a secret from his wife. One day, though, she reveals that she knows he's cheating-- she can smell the scent of another woman. Tonuno would eagerly divorce his wife, but he can't bring himself to do that to his little daughter. Will he be able to break it off with Moemi?