The Name of a Monster

Natsume meets an old shrine god, and is forced to help her return a mirror to a youkai said to bring disaster. As it turns out, the youkai in question turned out to be Reiko, Natsume's grandmother, who the shrine god mistook as a youkai. Reiko had lent her the mirror so the shrine god could save an old tree, but parted after Reiko learned she was a youkai.