Sei Yariman Gakuen Enkou Nikki

Based on a doujin game by Orcsoft.

A successful businessman finds himself in the middle of a life crisis. His wife and daughter left him making him question the purpose of his hard work. A young woman suddenly approaches him one night and offers him sex for money. He discovers the joy of sex after being celibate for many years and realizes that age is not a hindrance to start a youthful adventure.