Natsume's Book of Friends, Vol. 21

Nyanko Sensei hasn't been home in days, and Natsume is starting to get worried. He knows Sensei left in a party mood, but he has no idea where his friend and bodyguard was headed. And now there are rumors of evil spirits from the east heading to the local forest. Are they related to Nyanko Sensei's disappearance, and will Natsume have to face this threat all on his own?