None of you bothered to read the text for the scene did you???
The werewolf in question is the player.) Although the dialogue earlier questions if you wouldn't mind her having an open relationship, has is common in games of this genre it is explicitly explained that the MC wolfing out is his territorial instincts. Don't me ask how that works, it hasn't be explained yet and likely has to do with the area the MC is from however it does.
You literally can be the only guy any girl in the series can have sex with, or not if that is your choice, there is no unavoidable ntr.