This is a fairly simple, short adventure "game."
Younger brother needs a tutor, so his older brother's girlfriend comes to help him.
He then proceeds to sexually assault her in her sleep which leads to the next and then the next scene. There are maybe about 5-6 "days" worth of these scenes if I remember correctly.
Considering how short it is, and the fact that the boyfriend is basically not present so there really is no feeling of NTR, I wouldn't recommend it. It's not bad, per se, it just isn't anything special.