Unforgivable! A Total Lack of Respect!

is episode 90 of the original Naruto anime.

Synopsis
While Tsunade was having dinner that night, Jiraiya and Naruto arrived at the same bar. Suspicious of Jiraiya's reason for looking for her, Tsunade asked what he wanted, to which he replied that Konoha wanted her to be the new Hokage. She immediately rejected the offer, saying that anyone who would willingly take the title was a fool. Naruto, enraged that she would disrespect the title of Hokage and those who had held its position so bluntly, challenged Tsunade to a battle. The two stepped outside, and Tsunade sent Naruto flying with just a flick on the forehead. Then she asked him what made him care about the Hokage so much. Naruto replies to her that his dream is to be Hokage someday. Tsunade then thought of her two most beloveds, Nawaki and Dan and their hopes of being Hokage. Naruto noticed she had lowered her guard, and unwilling to give up, he readied his imperfect Rasengan for an attack.