Mama Haha wa Musuko o Aishiteru! ~Okaa-san ni Amaete Ii no yo…Rinko Mama no Ecchi na Osewa Jijou~

The heroine, Kurata Rinko, lives with her son, Shizuya.

Shizuya is the child of her late husband, and even though she is not blood-related to him, she thinks of him and loves him like her own son.

But one day, she finds in his room, a naughty book about incest…!?