Natsume Yujin-cho Season 2 Episode 13

Natori tells Natsume of a well near the mansion that holds a group of Oni. They are calling out to any Youkai. He also learns that Kai came down from the mountains to free the Oni. While looking for Kai, Natsume sets off one of Natori’s traps in the mansion. Kai saves Natsume and heads off to kill Natori. Natsume follows him,to save Natori from getting killed. After he encounters him, he is forced to make an important decision: Which ones are more important to him? Humans or Youkai?

(Source: Wikipedia)