Sei Yariman Gakuen Enkou Nikki The Animation

According to a doujin game by Orcsoft.

A prosperous businessman finds himself in the middle of a lifestyle crisis. His wife and daughter left him producing question the intention of his work. A little daughter woman suddenly approaches him recognized and offers him sex for funds. He discovers the industry of sex after being celibate for several years and realizes that age is not an hindrance to begin a tender adventure.