From the front as well as from behind - well, absolutely flat woman. Only one advantage is obvious - well-designed orifices. And of course due to the flat buttocks it's very convenient to pull your partner in the anus, even without bending her over. And I don't see anything else interesting in this lady! The man is basically of age, so probably the determining parameter for him is the age of the woman and the possibility to work her anally!
I have always been attracted to oriental women, especially Japanese women. I have read books about geishas and other traditions, maybe that is why they do not go out of my mind.
In fact, the Japanese sex culture is very different from the Slavic and European. Maybe that's what attracts them.
The girl blew the guy off because he can't kiss or fuck. He's still a virgin. So the mother is right - the daughter should help her foster brother become a man. And mama wouldn't wish no harm on him. Lucky the kid's got such advanced parents.