Through the Autumn Wind

On the way home from school, Nishimura and Kitamoto spots Natsume on the bridge acting all weird and falling into the river below. After seeing Natsume fall, they panic and rush to Natsume's help. Later that night whilst nursing Nyanko-sensei, Natsume's bag starts to twitch and a stone yokai crawls out of it. Apparenly, Natsume picked up a weird yokai whilst he was in the river.