Natsume's Book of Friends Season 4 Episode 6 The Other Side of the Glass ( Air Date 2012-02-07 ) Genre Animation, Comedy, Mystery category. Overview "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…".