I played it and got the good ending and the fun ending..and now I really hesitate to call this an ntr.
The MC is an idiot who doesn't care about the girl, who even says herself was bro-zoned. They aren't in a relationship and even then, the mc can see her getting bdsm-finger-banged and doesn't give a fuck, so there's no emotional rise out of him. The only way the mc falls in love with her and starts a relationship (maybe?) is with player input, and at that point she's with you, game over, no getting ntr'd..
There is however some level of ntr..in that she's "cheating" on the other slobs that want her, simultaneously, but I hardly think that matters.
Edit: Still good art and fairly entertaining tho..just saying I wouldn't call this NTR.