Natsume is jumped by a group of Youkai trying to steal the Book of Friends for their master. Once captured, Natsume discovers that an old problem is back in a big way.
It sounds like they came after 
the Book of Friends.
Parece que llegaron porque 
oyeron del Libro de los Amigos.
Parece que han venido porque
oyeron hablar del libro de los amigos.
E parece que estão atrás do Livro dos Amigos.