Yamahime No Jitsu Vol. 1 山姫の実 第一巻 M江

The protagonist Kazuya lives with his mother, they are a family of only two. One day we wants to buy a laptop but his mother is against it, however Kazuya still buys the laptop and is keeping it a secret form his mother. Of course as soon as he gets it he starts searching for adult websites, he randomly chooses one and when he enters the website he goes into a shock because the woman that appears before his eyes in all kind of erotic situations looks a lot like his mother. The website features only that woman being trained by a middle aged man. Kazuya immediately begins to doubt his mother since she has also been acting strange lately...