About the appeal of NTR, I'm guessing it's for cucks who enjoy mental torture? But it ain't really torture if you're enjoying it...
4th one however, I can easily answer with a resounding "No"
Because it is a clickbait manga. Just the naming is clickbait. I've started to read it solely because of the clickbait.
I see NTR as a name for serialized manga -> Thoughts "Wtf? How can this be? WTF it is above 7/10"
Stopped reading at chapter 36, my personal rating in my library 3/5.
1/5 is to never touch this shit, simply because it is physically un-readable due to structural problems.
2/5 Structurally passable but very bad
3/5 Lost in mediocrity of thousands titles in my library, chances of reading it are close to 0. (Only if manga production ever stops)
It's not good. ThirtyDigit is correct in his analysis. For me personally any form of NTR is bad, with very few exceptions (i actually have a few titles where i want MC to be NTRed). Instead author NTRed a decent MC.
There are people who deserve to be cheated on and i find it morally dubious but passable. Here? It feels that author really doesn't have friends or any understanding of friendship.
FYI: Quite a lot of NTR authors are women, NTR(Cheating) is a genre more popular with a more female auditory. Reason is fairly biological, sexual infidelity is less critical to women than men biologically (Children and in many places demands from men to take financial responsibility). Mere 100 years ago it was impossible to know if it was your child and infidelity was ingrained in us as for thousands of years as something unacceptable (more in male parts of population).
Even today with our technology there are quite a big amount of children being born not to their on paper fathers.
Infidelity(NTR genre) would be more acceptable if there would be true equality between men and women and children would be mandatorily tested for paternity and biological father would always take responsibility.
So any guy who likes to cuck other or likes being cucked is a magical unicorn. A person who brings instability to our society a deviant of great magnitude.
The problem why so called vanilla guys rage on NTR so much is logical. People who call other "vanilla" are people so far up their porn addiction that they are probably too damaged to get off from something normal.
Vanilla guys logic is sound simply because NTR(infidelity) happens in real life and has a lot of problems and consequences. In Japan laws are still good, cheaters must pay and custody goes usually to the non-cheating parent. In the rest of the world, courts favor cheaters (i.e bad conduct isn't punished).
Lastly cheating sex is sweet (sometimes affair partners are worse that spouses in terms of sex) simply because you do not share LIFE BURDENS(That heavily encumber and worsen relationship) with affair partner. You take only the best and sweetest moments with affair partners thus it feels intoxicating. The reality though hits stronger when you are found out and forced to share life burdens with affair partners and you understand that "sweetness" was illusion and you just fucked up not only your life but possibly lifes of 2 families (minimum). Even if not found out and you just naturally get together with affair partner, in a lot of cases this doesn't work out. It wasn't greener on the other side of the fence it was actually worser, you got together with your ex because you liked both the life and the romance, you got together with affair partner only because of the romance and didn't vet them for life compatibility.
tl;dr I dislike the NTR in this manga. It's not the NTR, it's how the NTR is done. It's weird, distasteful, and annoying that Naoto is fucking women that Shinji is interested in cause they for some reason all have ulterior motives and are trying to take advantage of him, and Naoto simply needs to fuck them to stop them.
You don't need to read much between the lines to realize that Naoto has some very deep seated issues about women and is probably a rather unreliable narrator.