Don't approach this game thinking it's going to be like literally any other RPGMaker game on the site. Think of this more like an actual RPG with occasional lewd scenes. As far as gameplay goes, this is probably the highest-quality game on the site, and in my opinion, the highest quality one put out by any independent developer. To answer in order:
My last playthrough was in 0.41.4, has 32 hours in the main save, and didn't even reach the end of the content available at that time. Maybe I was playing through slow, but that's still a lot of playtime. Like I said before, this is an RPG first and foremost, and the worldbuilding in it is top-notch.
Depending on your viewpoint, there's very little mind control involved. Corruption is a more faithful description of what you're doing, although in the strictest technical sense, it's mind control. If what you're wondering is "How often does the MC smash the brains of women to putty in order to fuck 'em silly?", the answer is: I think there are exactly two options for that? And neither of them have to be taken. You don't have to mindwipe anyone you don't want to.
I didn't personally find myself having to grind, but I also didn't care too much about always having the latest and best equipment. It is tough at times, especially for the optional loot fights, but the combat system is robust enough that, with smart play, I'm confident you can get through the main story at least without having to grind at all. I haven't even seen the optional dungeon yet, but I'm guessing that'll probably need both grinding and an optimized party to complete.
Like I said in the opener, though. This is a game first and foremost, and the porn is secondary. If you're looking for something you can fire up real quick, rub one out to, maybe finish in a few hours, this ain't it. If you're looking for an actual game with incredible writing and a lot of thought and love put into it, this'll be more your speed. I suggest giving it a shot anyway if you like old-school RPGs.
