Anal Mama ~Ushiro no Ana wa Musuko Sen'you na no~ by Appetite - Adult Sex Game

Ayumu and Touka are son and mother-in-law.

One day, Ayumu asks Hiiragika about sex.
He watched as his father and stepmother had sex with each other.
Wanting to answer this serious question without muddying the waters, Hiirahana first tests Ayumu's knowledge.
"Have you ever masturbated? Masturbation can make you feel like you've had sex."
But Touka has more to learn about sex than just masturbation.