The Duty of the Guardian of Rain is the 180th episode of the Katekyo Hitman Reborn! anime.
Ugetsu Asari tells Yamamoto that he will give him a second chance at the trial the next night but will not have a third if he fails and disappears. The next day, Uni transfers into Namimori Middle School under the instruction of Reborn , while Tsuna and his friends attempt to find out why Yamamoto failed his trial. Meanwhile, Bianchi, I-Pin, Kyoko and Haru visit Chrome Dokuro only to find out from Ken Joshima and Chikusa Kakimoto that she has been missing since the day they returned from the future. That night, after receiving advice from his father, Yamamoto arrives at the shrine where Tsuna tells him to not push himself. Yamamoto and Asari engage in battle and Yamamoto prepares to deliver the finishing blow but suddenly stops, realizing what his father said. Asari then declares that Yamamoto has passed the trial and explains that Yamamoto failed the trial last time because he attempted to betray his heart and kill a person who was defenseless. They then both compliment each other and before leaving, Asari tells Yamamoto the Rain Guardian must not run dry and must keep his friends together.