The whole corruption debate is still going on?
1. There are routes based on your decisions
2. Corruption typically affects dialogue and unlocks extra scenes like anal, threesomes and public sex. Having looked at the game files, the highest corruption that can alter dialogue is 25-30. Beyond that, it does nothing.
3a. Some NTR scenes are gated behind corruption so even if you pursue the ntr route, nothing will happen if corruption is not high enough
3b. No matter how corrupt a girl is, there is no ntr as long as you, the player, don't make the choices that lead to ntr.
4. Each girl also has a "likes NTR" tracker associated with them and the more NTR scenes you do the more willing they are to engage in NTR (this especially affects Kate).
Regardless and in summation, it is still your choice in everything that happens. You can also choose to not corrupt anyone if you want, just take strong anesthetic (though this will lock you out of a lot of content)
Corruption as what has been stated multiple times simply lowers their inhibition as well as making them more sexually active. This is why on certain love routes a higher corruption is required in order to break their resistance to cheating on the MC. If there is some unforeseen downside to corrupting them (which is not NTR because again that is driven by player choice) I don't see that as going over well because pretty much everyone corrupts the characters in order to access more scenes. The entire theme of the game is corruption so that is very unlikely to happen.
I wrote this quickly so there might be some errors in logic but the people who are going to understand will understand and the people who don't won't ever be happy so.