Natsume Yujin-cho Season 5 Episode 3

The Letter from the Exorcist

Natsume finds a letter addressed to him from Matoba. Walking in the forest, he loses it when an amateur exorcist seals a yokai in a pot. Noticing the weak seal, Natsume and Nyanko-sensei take it to Natori's condo to re-seal it. When Natsume returns home he sees Matoba and learns the letter was a request for Natsume to attend a meeting of strong exorcists to weed out the person who has been targeting exorcists.