Natsume receives a letter from Matoba, an exorcist whom he's had unpleasant dealings with in the past. The world of exorcists is a dangerous place lately, and Matoba wants Natsume's help. Natsume wants to refuse, but Matoba threatens to reveal Natsume's powers to his adopted family, which would spell the end of his peaceful life.
There are also certain methods of exorcisms 
and contracts that are forbidden.
También hay exorcismos
y formas de pacto prohibidas.
Também foram proibidos alguns
métodos de exorcismo e alguns contratos.