Naruto: Shippuuden - Season 3 Episode 16 -

Furido releases Sora's seal, and tells him the truth: Sora is a pseudo-Jinchuuriki. The chakra that had leaked from the Nine Tailed Fox when it attacked Konoha 15 and a half years ago was harvested and implanted into Sora. Sora's father. Yamato, Sakura, Kiba, Lee, Ino, Choji and Shikamaru also turn up. Enraged, Sora wants to destroy everything, and turns into the Three-Tailed form of the Nine-tails. However, Yamato is unable to restrain him, because he does not have the First's necklace on him.