Uchi no Tsuma ga Hibi Kirei ni Natte Iku Ken ni Tsuite

A married woman (protagonist) tells her personal story of how she began sleeping with a wealthy young lover to pay her husband's debts... but over time, somehow, she fell more deeply in love with him.

An adventure style story, starring Eri (the wife), her lover, and her husband.

[From DLsite English]