Natsume overhears whispers that a powerful youkai is reviving, later that evening he is trapped in a bottle as an offering.  Humans can’t see or hear him, so Nyanko-sensei decides to help the “best” way he can…
You owe me big for this, Natsume.
Te cobraré caro, Natsume.
Haré algo por ti, Natsume.
Você me paga por isso, Natsume.