It is called, "The Tale of the Gallant Jiraiya." In the tale, Jiraiya, who was proficient in toad magic, was married to Tsunade, who was able to turn into a snail. Jiraya's one time follower, Yashagoro had been overcome by serpent magic and changed his name to Orochimaru, and then became Jiraiya's archenemy.

That's about it.