Natsume's Book of Friends (2008)

S5E5 It Must Not Be Bound

Natsume attends the exorcist gathering to assist Matoba in locating a youkai. However, he soon realizes that the scenario is far more intricate than he anticipated. This particular youkai can duplicate itself to take control of others, and only Natsume has the ability to identify those who are possessed. Together with Nyanko-sensei, he navigates the corridors, both feeling uncertain about their presence at the meeting.