Koro-sensei and the students of Class 3-E travel to the northern cave to confront Karma Akabane the Red Devil, who is known to be unlucky when he is cocky, especially when washtubs randomly land on his head. Inside the northern cave, they are soon surrounded by Mushroom Kunudons, but Karma makes an unexpected appearance. Even though Karma falls through a trap door, he comes back up and tries to catch Koro-sensei. However, Koro-sensei takes Karma to a hot springs in order to convince him to join the class.