Be careful, this is a dangerous wish!
By taking the literal meaning of NTR as a definition (Netori + Netorare), since no one is in a stable relationship in this game, i see zero leeway for NTR. Unless one of the guests is married
Other men could be sexual active, but only one of the male guests looks attractive in my eyes. I would have no problem with that. Assuming it's tied into a good story, I'm actually up for NTR, sharing, swinging, and so on. So, for me, other men and women are welcome to be sexually active in a game. But I'm sure I'm almost alone. The forum generally likes to go stormy when a different penis appears than that of the MC.
Kay on the other hand has already been actively interested in several women. So there will be sharing. That's the way it is: women are tolerated, men are not. I would wish it differently. But the forum is not that far yet
As far as I know, the game is not planned that way (with the exception of Kay). And most fans will also be strictly against it. They will not accept anything other than their harem. So, I doubt your wish will be fulfilled.