Lust in the Rain.

The story centers on Yoshio, a poor and struggling manga artist who lives in Kitamachi. He is sent by Oyaji, the landlord of his apartment who is also engaged in other shady businesses, to help a novelist called Imori move in, and meets a recently-divorced woman named Fukuko. Yoshio is immediately bewitched by her beauty, even though she is already seeing someone else. In the meantime, Imori establishes an advertising agency, borrowing the name of a larger agency from the wealthier Minamicho, in order to sell his novel. Yoshio ends up helping with Imori's efforts, and somehow Imori and Fukuko come to live together with Yoshio.