I won't leave a review yet as I only played like an hour and a half but already I can understand some of the bad reviews out there.
The game is grindy in a bad way. I enjoy grind but not just for the sake of it. Why would I go to the cave until I have max strength? That means what: just spamming go to the gym and workout, go to sleep, until max strength. With a few in between working for some money. Is that a game loop that sounds enjoyable in any sort of way? Same with the other stats. I only increased strength intel and mechanical until now, so can't comment on the rest yet.
Can't comment on the corruption side yet as the potions of corruption cost at the start way to much to craft, maybe I have to play more to see how that goes but again, the game is designed to not make you interested in exploring or spending time with the girls at the start. You gain nothing from it, from what I can tell so far. The only stat increase that seems to do something else as well is mechanical with friendship points with Valentina (again, from what I've seen so far).
The cave: The fact that the encounters are random and there aren't monsters you can engage or avoid is one of the bad ways to do fights in rpgm. That means that at any time you can get jumped and killed if somehow you are left on low hp. I managed to get to the third floor, no easy way to get out. You would have to trudge back through all the previous floors (which would be bad by itself but add to that that you would get assaulted by a lot of monsters, it makes it even worse.
These are just some bad game design decisions I encountered so far. The biggest one so far though is that the porn content and the progression of the game are not linked. This is a game where you have to increase your stats and the porn is a side reward.(again, maybe I'm mistaken and have to progress a little more to discover it's not all like this). If, as you stated, you want to make a game that stands on its own and not just sex scenes, ask yourself this: would anyone want to play this game without the sex scenes? Would it be enjoyable enough by itself?
Just some thoughts after my first time trying it. After I saw that you can't get out of the cave unless you walk back through monsters or lose, lost, spent two days in infirmary which triggered the int drop (how could I know so that I can train int in the morning before monster hunting, I know now) I decided to give it a rest for the day. Will try again with new nerves and see if it has any redeemable qualities before making a final decision.
P.S.
Forgot to mention:
Why do we have flirt, sex, sex vulgarly(bad translation btw) from the start?
Unless I have no idea what stats, they fail and you loose friendship. How can you even approximate when you should flirt? Is it a hard limit, or does it have a chance to succeed based on stats? Would it be better for each option to only appear if you can succeed at it? Why penalize the player for something he has no idea if it would work or not? (if you can give percentage chances for each option during selection, that can work as well).