I agree dude, its just a harem story with the idea of incest, not even talking about the "Oh but its wrong, so why do I want to?" Or if it is, its just like one or two lines.
I think the only difference in Erotic Vs Porn for games is if we see sex, oral or otherwise. A lot of erotic games will push for everything up to sex, then fade, before just picking up where it left off.
The less is more approach works if you want to hide things from the viewer for tension, its...