'NTR', or 'Netorare', directly translates to 'cheating' in Japanese.I think you're the one who's crazy. You don't understand the ntr tag at all.
"But the MC doesn't have feelings for her so it doesn't count"
"But the MC wasn't there to see it so it doesn't count"
I know just by seeing your thoughts. Take for example a doujin called chitose.
Not a boyfriend, not a husband, not a close friend.
If the context is correct, it still counts.
You can't 'cheat' on somebody, when the character partaking in another relationship doesn't have a romantic relation ship whatsoever with the MC?
It can be argued that in this case it's 'Netori', or 'Reverse NTR' - as the MC will 'steal' this girl from her previous relationship. However, the relationship will be terminated after the point that the MC will be able to romance this character.
I understand that people have issues with this concept in general, and I want it to be abundantly clear that I will accommodate for that as much as possible (skippable lesbian scenes, the option to not romance certain characters).
At the end of the day, this is a planned tag. It isn't even in the game yet. When I do eventually end up including this, I will make sure to do it in good taste.