So gonna echo a lot of others, years after the fact. Having just finally come across this and played through, it was definitely an incredibly strong NTR experience. I don't really expect to spark discussion / be sharing feedback so at this point, but still going to share a lot of thoughts, to get them down and out of my head more than anything.
One of the biggest appeals of NTR arcs to me is the sense of encroaching inevitability they have in the build-up, being able to see as the viewer that there's no way out. I think that's why the 'NTR logic' that tends to crop up at least a little bit can be so grating; if it seems like things only move forward because of contrivance, or people being complete idiots, or otherwise acting out of character, it undermines the sense that there was no escape.
That said, I think this game did *really* strongly at avoiding those pitfalls, if not entirely. The rest of this will be (a whole lot of) more specific thoughts on each of the four 'heroines', including where things are stand-out examples of working, as well as where they fall a bit more flat. (I'll note that the one ending I haven't actually played through is the NTR end, though I doubt there'd be anything in that that would suddenly overturn my thoughts from the rest of the game).
On the extremely off-chance that the dev sees this (and even more off-chance that they actually bother to read the short-novel series I ended up writing above), I'll end this on the note of reiterating that I had an absolute blast with this game, and that even with the points I critiqued, I found it to be easily one of the strongest and most internally-consistent examples of NTR writing I've come across. I'm going to be taking a short break, but afterwards I'm very much looking forward to moving on to Chapter 2, all the more so knowing that Chapter 1 was their first experience creating a game like this, so they'll have the opportunity to have built on that foundation for an even stronger showing in the second.