Torottoro no Oyako Ren'ai ~Okaa-san no Toro Kao ga Kawaii~

Shinya, the protagonist, is a ronin but spends his days just fooling around. One day, while hanging out with friends in town, he's spotted by his mother, Shizuno, who drags him home. After his friends keep teasing him, “Your mom's hot!”, Shinya starts becoming conscious of his mother.

The next day. Shinya, undeterred, is about to head out again when invited by his friends, only to be caught by Shizuno. “Please. Study” she asks. While being lectured, he says “I'll study if you show me your tits!”

Taking his joke seriously, Shizuno undressed and showed him her huge breasts! Blinded by the sight of his mother's breasts after so long, Shinya demanded a titjob...

Then, Suddenly high from touching a cock for the first time in years, Shizuno went wild, Easily making him cum with a fierce blowjob. Unable to resist his mother, Shinya pushed Shizuno down and ended up having sex with her.

[From official site]