I sorted "rpg" games by rating, and was simply shocked to see the three dozen games rated above this one. Admittedly I have not played all of those games, but I have played more than half of them, and the vast majority of them can not compare in any logical, objective sense.
Given that I played Harem before almost all of these other games, I thought perhaps my perception was just askew in hind-sight. So I decided to go back and replay this to see if my memory was accurate - if anything, seeing it again after having so many other, higher rated, rpgs only makes me see the quality of Harem all the more.
I was no fan of the art, but compared to many games, it is great. Further, given the utterly massive number of images there are, a more high-res form of image would be extremely difficult.
The story has some flaws, but again it is far more compelling and complex than the vast majority of games, and it is gigantic already.
The behavior/choices of the MC have actual weight, not only to the narrative but, rather amazingly, to the behavior and personalities of all the PCs and even NPCs.
The characters absolutely shine. Almost all of them (and there are tons) are well defined, uniquely lovable, and most surprisingly for a "harem"/slave game - all have agency as individuals.
My only initial complaint was the game-play and skill mechanics, but that is currently being addressed in current updates.
There is a level of philosophical introspection that resonates through the darker more "perverse" narrative elements, which for me is the really impressive factor. It manages to supply an lot of sexually dominant fetish scenes while bringing into the mind the more human (or even humane) aspects of sexual submission/domination. This is something I never expected to perceive in a NSFW game, and indeed I have not seen anything else similar thus far.
There are several "under-rated" games on this site, in my opinion, but this one is probably the most so.