What I think is happening to Stiles is that he is awake at times, but the other times with the whole “WAKE UP” thing is him in a state of possession, not being conscious. He could either be a serial killer(William Barrow style) or A Kitsune or whatever, but the point is that in the hallway promo it says “This isn’t you” then “This is you” And he obviously did something bloody(around the mouth) which could be him attacking(biting) somebody while he isn’t awake, and his subconscious is telling him to wake up.
I also found this
Hoshi no tama
Depictions of kitsune or their possessed victims may feature round or onion-shaped white balls known as hoshi no tama (ほしのたま, star balls). Tales describe these as glowing with kitsunebi. Some stories identify them as magical jewels or pearls. When not in human form or possessing a human, a kitsune keeps the ball in its mouth or carries it on its tail. Jewels are a common symbol of Inari, and representations of sacred Inari foxes without them are rare.
One belief is that when a kitsune changes shape, its hoshi no tama holds a portion of its magical power. Another tradition is that the pearl represents the kitsune’s soul; the kitsune will die if separated from it for long. Those who obtain the ball may be able to extract a promise from the kitsune to help them in exchange for its return.”
Everybody keep watch for something like that.