The Door of Memories

Natsume, accompanied by Nyanko-sensei, set out to visit his old home. He visits a relative to pick up the key to the house, but is being followed by a youkai who wants him to draw a mouth for it. He leads the youkai away from the home of his relatives and Nyanko-sensei drives it away. When the two get back on track to finding the house, Natsume is suddenly attacked by the youkai and becomes lost in old memories.