Joushi no Tsuma wa, Motokano Deshita: Iyagari nagara mo, Makura Eigyou ni Oborete Iku After 5

Based on the erotic game by Appetite.

Tomoki Haga and his college sweetheart, Shiho, were supposed to be the best of friends, but one day she suddenly left him. A few years later, Shiho reappeared in Tomoki's life, this time with the title of head of the accounting department and, to his dismay, the wife of his boss. Tomoki, seething with hatred, confronts her with a video he took of Shiho in the past and offers her body to strange men as a tool for trade. Shiho's body, however, remembers the days of pleasure with Tomoki, and her hidden lewdness begins to blossom!

(Source: parabook, translated)