By now, yes. But I don't see how the developer would center the story around a cursed forest that is shown to taint everything it touches, and then give the main cast a free pass from it. It's just convenient and allows ridiculous things to happen, but again, I don't want it to be the reason Valla cheats. If it serves as a catalyst, though, I am fine with it.
(This is from a writer's perspective, by the way.)
On the other hand, when you say that you didn't pick any dialog that would indicate how the corruption might have affected the MC, I agree with you... but that doesn't mean that the developer couldn't have dropped hints here and there in support of a later awareness. From experience, I can say that's what makes a story feel naturally intrincate instead of plainly idiotic. Time will tell.