Inside the Mist

is episode 100 of the Naruto: Shippūden anime.

Synopsis
Guren was rendered unconscious, and began to relive her past as Naruto was caught in an illusion about Sasuke. After Kakashi found him, Team Kakashi and Team Kurenai concluded the mist around them caused Genjutsu courtesy of the Three-Tails. After Guren woke up, Yūkimaru suffered another fever and passed out. Tsunade heard of the Three-Tails, and assembled Shizune, Ino, Tenten and Lee to go and seal it before the Akatsuki could. Naruto and Sakura talked about the home that people should return to, before Naruto headed off to find Yūkimaru.