Naruto Shippūden: Season 2, Episode 48

2 - 48: Bonds

Yamato and the team enter Sai's room and confront him while Kabuto makes his way there as well. Sai tells Team Kakashi that not only was he to help with Konoha's destruction but also act as a spy against Orochimaru. Yamato reveals the secret of "Root"- its members were trained like Kirigakure's students in that they had to kill their friends so as to eliminate their emotions. Sakura returns Sai's book to him, remarking that he still has emotions because he treasures it. Sai then tells the group about his bond with his brother. Finally the team decides what to do about Sai's betrayal outside the lair. In doing so, Naruto tells the group about his own bonds and about how far he's willing to go to bring Sasuke back.