It wouldnt be a spoiler because it obvious nina is cheating lol, no really surprising.
I dont need to read two posts because what matters is f95zone's definition of ntr and for it cheating on MC is enough, nothing else is required, context no important.
So when it is revelead that she is cheating this will get the ntr tag regardless of your personal definition of ntr. Would not be the first game with the ntr tag, that its dev says it has no ntr.
But thank for answering, I think i have more of an idea now about what game is about and thats all i wanted