"Inheritance! The Necklace of Death!" (初代火影の遺産 死を呼ぶ首飾り, Shodai Hokage no Isan Shi o Yobu Kubikazari) is episode 91 of the original Naruto anime.
Naruto tries to hit Tsunade with his not yet perfected Rasengan. Tsunade punches the ground, creating a fissure that Naruto is trapped in, negating his attack. She then berates Jiraiya for trying to teach Naruto a technique that he couldn't possibly master. Naruto insists that he could, and bets that he could master it in three days. Naruto's personality reminds Tsunade of her deceased loved ones, so she accepts the bet, giving Naruto a week to master it. If Naruto won, she would accept that he could become Hokage, and would give him her incredibly valuable necklace that had originally belonged to the First Hokage. If he loses, then she would get to keep Gama-chan, his purse full of money. Naruto accepts her terms and decides to begin training. Later that night, Jiraiya comes to sit next to Tsunade at a shop, and the two discuss her lover, her brother, Naruto and Orochimaru. Jiraiya reminds her that her loved ones all died for the village, and that if she helps Orochimaru, their deaths would be in vain. Meanwhile, Shizune talks to Naruto about Tsunade's past and about the history of the necklace. Shizune explains that the necklace wasn't an ordinary necklace, and that if anyone except Tsunade wore it, that person would die. While Shizune was talking to Naruto, Tsunade is sitting on top of the gate of Tanzaku Quarters, thinking back on her brother and her lover, both of whom died and whose deaths she could not prevent.