Ok, let's see. Part II had Headpats, Handholding, proteccting and amazing romance progression (for an h-game). This one has... generic corruption/prostitution and rape.
After Gran Ende II, first and third parts just feel... generic. There is already a myriad of h-games of "heroine corruption" type and they all follow the absolutely same boring formula. There is no special appeal or advantage over others.
Gran Ende II was a breath of fresh air, pretty much this publisher's gem. Why they wouldn't stick to the the same formula in part III is puzzling.