Pretty sure the Yokai you listed were Petite Soeur's way of making a joke. XD Yokai most likely includes the Yoko class (Inari and Kayou) and the Nurarihyon class itself. Bashira might be included due to it being a running joke in the event's story. Thetis and Mireille are supposed to be humans are they not? I guess the rule of thumb is to look for characters with kemonomini ears. Ada the plat rogue might count too.