I don't think that scene is NTR, the MC doesn't date her, she's his girlfriend's sister, but not his girlfriend. But I guess many who don't like NTR will be just as bothered.
For me it's a voyeur scene, which, along with those of dreams, matters little to me. I have a complete lack of interest in watching voyeur scenes, lesbian scenes, and sexual dreams scenes. Personally, I would rather be able to skip or avoid it, but being able to use the appropriate button to skip it and not see it works for me too.