A Question for the Tekken people

Okay, I kinda suspect the Tekken canon/story is just so hosed that there's just no good answer to this but uh, do we know how possessed Kazuya Mishima is?

I mean, I know the answer is yes this man is chock full of Devil but how much control does he have over Devil?

I've been trying to figure this out for Fic Reasons, because wow did the Tekken 8 trailer bring this fandom roaring back to me at full interest, and it's bugging me. Below is the evidence I can find: ( in which I try and fail to make sense of the Tekken rules on demonic possession... )