The game has been tagged NTR by the website because there is Netori and because on the description it was said the girls you chose to not romance can have their own life (which is not really NTR anyway). And most people already said on the topic that the NTR content is minor and always clearly avoidable.
I understand some people prefer vanilla and don't want to deal with that, for those, I have clearly indicated each time if a choice was going to lead to possible NTR. There are not many options like that, and you don't even know they will exist when you focus on romancing one girl during your playthrough. It's when the player fools around that he can find the options for NTR, as you need to have low points with the girls to make those options appear.
To sum up, I don't really need to make a switch on/off NTR, because it more or less already exists inside the game by playing romance routes.
On the other hand, the last update
showed the premise of a new route : the evil route. I chose an obvious name so I don't need to explain it more. If you are going for vanilla, obviously do not jump there 
ever. Again options leading to those are pretty obvious. You can totally avoid that.
