TL;DR: I apologize to the dev for a harsher previous review. The game is much better than some other reviews claim: there's plenty of content beyond simply getting cucked, but it's true that you need to know what every choice does to properly keep control of the plot and choose carefully.
I rescind and correct a negative review I had written earlier.
After quickly scouring through the entire game and every possible option (took me a while), I see now that the whole "your choices don't matter" thing isn't actually true.
Yes, the game is rushed at the end, that's pretty much clear and it's something the author has acknowledged; the endings are pretty rushed and they obviously don't cover most of what should've. The biggest problem the game has is that the 1st Part opens up a ton of options and subplots that get progressively less attention during the 2nd and get outright abandoned at the 3rd. Some things that were foreshadowed never happen and in the end the story gets focused so much on Clara that you forget about the other 'love interests' (although I don't think if they should even be considered that since you only get to sleep with them at times).
Still, there's not the same level of disconnection between choice and outcome as others have pointed out (and me myself thought before); that being said, there's some in the game. For example it's a bit weird that you can't really stop some things about Clara from happening, like her kinks activating. The good thing, though, is that if you really go straight for the Ending #1 (lowest Lust possible for Clara), it's still pretty coherent; it actually feels like she has some autonomy, developing her own preferences despite your wishes. Other endings feel a bit more forced, due to the speed at which Clara's corruption progresses. That's not to say others don't have it even worse; I'll be eternally sad that Amy had the misfortune of having this dev as a creator, the poor thing can't seem to catch a break.
I will say, the game is much better than I first thought, but you may need to replay it many times (or savescum) until you recognize that it's shortcomings are either the typical things you find in most of these games (rushed plot points and the like) or a product of not knowing exactly what you need to chose to get the ending you desire. A walkthrough mod would do wonders for all those that feel like they lack control in the game; I'm serious, you've got more input (and sex!) than what some other reviews (and, again, I myself prior) have stated.
All in all, solid 7/10, would fall for Ending #1 Clara a hundred times over.