Hahaoya Saimin Nikki ~Otto no Inai Aida ni...~

The mother is a well-behaved, modest, and chaste woman. However, since her husband is often away on business, the protagonist accidentally observes her masturbating.

He uses hypnosis on his mother, and succeeds in depriving her of her freedom.

"I'm going to tell your father!"

The mother is so fretful, but as the protagonist caresses her and uses sex toys on her, she gradually begins to let out a seductive moan.

[From official site]