Newlyweds [Kazuya] and [Misaki] live together with Misaki's mother [Eimi], and the three of them lead a life together.

One day, Kazuya returns home to pick up something he forgot and finds Misaki talking to Eimi about her sex life with Kazuya.

When Kazuya is discovered by the two, he asks his mother-in-law to teach him how to have sex with her.

[from official site]