Natsume Yujin-cho - Season 5 Episode 7 Distant Festival Lights

Tanuma invites his friends to an inn run by his relatives. While sweeping outside, Tanuma is greeted by an old woman named Ito-san. Natsume learns that Ito-san is a yokai that serves the Mizunagi shrine by protecting the mountain festival. Ito-san has come into the inn because another yokai has stolen the festival's white mask and has disguised itself as an inn guest. Natsume finds the yokai who stole the mask for the festival's power, and Ito-san exorcises her. Ito-san warns Natsume to keep her identity a secret until after the festival is over so she can complete the festival. Natsume says he will tell no one she is a yokai so she can stay in this town as long as possible.