Actually, now that I've read more about NTR and what it really stands for, this story isn't really NTR. NTR is almost specifically designed to hurt the reader. The manga I mentioned couldn't be further from that. If anything, what it builds is slow anticipation for a possible genuine romance.
Dunno where you read this from but NTR is a catch all term for netorare and netori and netorase and many more with neto-r_ words in japanese...
Basically its only definition is, 1 of the partner/coupled-characters/couple/in-love-with-another-person/husband-or-wife is sleeping with with someone else... Thus the word neto- which means to sleep with in this context...
The -rase, -rare, -ri and many others are the definition of the point of views of the lead characters and defining how they are sleeping with the other people...
In -rase for example, the couple both are willing to let one or both of them to sleep with other partners. Basically swapping partners...
In -ri for example, your view point is the MC stealing other people's partner.... Basically you romance the shit out of the person to steal their hearts away while sleeping with them....
In -rare for example, you either view it as the partner who see their loved ones being taken by some other people... This is the one genre a lot of people like and hate at the same time.... The cucking simulator....
There are more obscure ones but these 3 are the main ones in the NTR catch all term...