NTR is optional and not a base requirement... while some characters have NTR routes it's not the "true route" (neither is the Love route) handling characters differently in such a significant way seem wrong and likely cause to much trouble anyway.
Corruption lowers a persons inhibition and raise their sexual needs... it's not brainwashing a human to do something completly out of character, even less if it's something that threatens one live.
But companions are already optional, so that in turn means the NTR would also be optional, besides, The NTR i am proposing is entirely optional, take Kate into the woods, encounter enemies, decide if you want to win or lose, losing leads to some kind of NTR or something similar, I think that NTR does not need to be locked into routes.
I hate unavoidable NTR, it means less options.
I do not know about you but every hentai with corruption I have read always leads to the female losing their sense of reason.
E.g. I will never join you and fight to the death for you [insert antagonist] -- To -- antagonist sama i will fight for your dick to the day i die.
Not sure how far the corruption in this game goes but, if Kate's corruption, and maybe lust, is high enough you should be able to convince kate to acompany you into a forest for some extremely kinky play. Again, its entirely up to the Dev.