Let's kill off main girl Morii Ayaka and just make side character Tachibana the protagonist already.
Knowing how the author has done things so far, Takigawa is likely gonna be the third werewolf if no one else gets some character exposition.
If the third werewolf does exist, then it's probably like Higuchi said, they've convinced themselves that they're a villager - that sort of pathological liar is dangerous in this game. Even if the third werewolf is consciously aware that they are the werewolf, they're blending in with the villagers by denying themselves information about their partners, thus making their reactions genuine.
Edit: It's possible that they were crazy enough to not even look at their card, but I got a feeling the author wouldn't be able to convincingly pull that one on us.