In Natsume's Book of Friends, some of the human-looking Youkai wear masks, or at least obscure their sight. For example:
I am wondering if there is a reason for this as none of these Youkai seemed to be affected by their obscured vision. For Tsubame and Hotaru, they are both shown to be able to show their full face. And for Kiiragi, after she was attacked, we can see one of her eyes though her broken mask and there seemed to be nothing wrong with it.