I just think it just wasn't done very well, its not like there was a sign that said: pick this option to avoid NTR. And even if there was it wouldn't feel like an organic development of the story.
My main gripe is that there wasn't that big of an indicator that one of my choices would lead to ntr, I would have liked it more if an option would have come up when eavesdropping to either intervene or to stay and watch, that way if you decide to stay and watch you got put on the ntr path but if you instead intervened you got put on the romance route.
I also think that if you decide to intervene the tutor probably should get fired and get written out of the story as that seems like a logical result to being caught molesting your student.
One thing that I really dislike about games with optional ntr is that sometimes the romance route is just the ntr route but with some scenes cut to make it look like the mc isn't getting cucked, which just feels lazy. I hope that won't be the case for this game. I mean if that's the way it's going be done they might as wel make it pure ntr.