I personally consider a scene like that to be a hot lesbian scene and eventually an opportunity to get a threesome without even having to do shit for it and not ntr.
Now let's see if it's actually is ntr or not besides my personal pov.
vndb tag:
You must be registered to see the links
The games which contain the scenes with protagonist's female significant other being stolen by another female, should be given this tag.
It's important to note that due to the prevalence of "girl-on-girl is hot" trope, it's common for many VNs to throw in lesbian scenes between the heroine and another female. Most of the time it is not considered NTR due to the protagonist not minding or even encouraging the lesbian exploration of their significant other.
Only use the tag if another female clearly has a design to steal the heroine, and the protagonist experiences jealousy and other negative emotions associated with the netorare fetish.
I think the definition should be enough but let's dig more into it.
So by definition it would be considered ntr if one of the women's featuring the lesbian scene is an antagonist or just a random women who isn't a li already just like with most general ntr games.
Which is not the case in that scene so that scene shouldn't be considered ntr, that's why this thread cannot be tagged with it.
Now you asked if it would be considered ntr if it was a dude in place of Vicky
Yes most definitely because fortunately this isn't a gay title so any male in the game cannot be a LI of the mc and as such any male involved with any li in this game would be considered ntr.
But you can't relate this fact to that scene to prove that it is ntr.
