"Believing" (信じる, Shinjiru) is chapter 447 of the original Naruto manga.
With Yahiko, the apparent leader of the Amegakure peace-seekers, dead, Hanzō tried to eliminate Konan and Nagato. Nagato protected Konan and slaughtered Hanzō's men. He called upon the Demonic Statue of the Outer Path and tried to kill Hanzō too by bonding his body with the statue, but Hanzō escaped. Nagato severed his ties with Amegakure and adopted the alias of Pain, setting him upon the path to peace by world domination. His story done, he asks how Naruto would have done things differently. Naruto replies that he completely understands Nagato's reasoning but that he cannot accept it. Adopting Jiraiya's philosophies for himself, Naruto makes not killing Nagato his first step to achieving peace.