My final criticisms of this game: I'll say right away that I analyze the game as someone outside the game; I don't have the perspective of seeing how the protagonist feels or feeling jealous of the FMC. That's why I find the NTR weak. Basically, the MC has no romantic connection with the FMC before YOU decide to start the NTR. In fact, this is a very serious weakness. The NTR in this game is entirely a choice; you can very well play the game without any NTR occurring, just because it will start if you begin the heart events on the map. The NTR is only minimally interesting at the beginning of the events; after that, the FMC becomes hopelessly in love with the guys, and then the story becomes a boring romance. I don't consider it good NTR, but the strongest point of this game is the voyeurism. Yes, the game is more about voyeurism. It would be wrong to judge the game based on the weak NTR; the scenes are still good.
My final conclusion is a 7/10.