Tale of a Gutsy Ninja - The Jiraiya Ninja Chronicles

Jiraiya’s journey to seek out a student is postponed due to the outbreak of the Third Great Ninja War. Jiraiya joins Tsunade and Orochimaru to battle the Village Hidden in the Rain. Following the battle, the three ninja are named the “Legendary Sannin,” a title given to them by the enemy Hanzo of the Great Salamander himself.Source: crunchyroll