That's asinine. NTR is a fetish you weirdos online made. There's no elements of NTR. Leaf clearly did not see her that way. It's a common trope for older people in any form of media to assume young people are together. You weirdos are just obsessed with NTR and cucking. All coom brained.
First, when we talk about NTR here, it refers to a story element in this context. There are countless stories with that element to put the MC down in the beginning to make his/her rise to fame and power more interesting and also allow for additional contrast and plot points if the ex partner is met again later in the story.
That element is so common that there's actually a tag for just that on some sites.
This is NOT about porn in any way, so this is most certainly not about a fetish from anyone here, especially a weirdo. Seriously, if we wanted porn, we wouldn't have started reading this particular manga in the first place, lol.
Even if you dislike losing an argument, you shouldn't resort to insults and you also shouldn't mistake commonly used story elements for the readers' fetishes. That's just ignorant and insulting.
Stick to facts instead of insults, especially if you're convinced that you're right.
On that note, I did literally prove it to you, you can easily reread and confirm everything I said and explained in that regard. You'd just have to do it, I guess.
If you do, you'd see that the NTR element was briefly used there, but not focused on. Even if the rest of the story conveniently forgets about it in the future, that's a different problem.