Title: Tsuma no Haha Sayuri
Original title: 妻の母さゆり
Developer: Cattleya
Publisher: Cattleya & Dennou Club
Release Date: 2008-04-25
File Size: 250MB~

Getchu: http://www.getchu.com/soft.phtml?id=480945
VNDB: http://vndb.org/v2076

Description:
The main character is a white-collar worker. He has a wife, but she runs away from home. When he is at a loss what to do, Sayuri, his wife's mother, reaches out for him, "I'll replace her.... Please...." As he lives with her, he gradually falls in love with her, and so does she....

Screenshot + H-scene