ah, i see.
let me try putting it this way. to get as much NTR content as possible. should i try for high affection or get low affection?
Sorry if my reply didn't fully answer the question! >.<
For NTR content that involves the teacher, it'll be purely dialogue choice. Player will be able to let events play out leading to NTR or choose to stop it from happening.
If you wish to see the two girls who have NTR related stuff in their girlfriend route. You'll need to build up affection, the higher the more you'll unlock. The game will give big hints to which girls have that as their focus in the route, before you choose your girlfriend. But.. For those of you who wish to spoil it without guessing or getting hints leading up to it..
So to sum it up.
Teacher does NTR content based on player choice. You choose if it happens, no need for stats.
The girl's routes NTR content based on having high affection to make them your girlfriend. Need to continue building stats for select girl.
Hopefully this answers it ^^ There might be more NTR content in future updates. But that's the goal so far, we can always go back and add or expand on content later.