Six-Tails Unleashed

This anime-only arc of Naruto: Shippuden runs from episode 144 to 151. It examines the bond between a master and pupil, the Six-Tails jinchuriki Utakata and the girl Hotaru. The Fated Battle Between Brothers comes before it, and Pain's Assault follows.

When bandits known as the Magaki Group storm a mountaintop stronghold, Hotaru flees with the drifting ninja Utakata while her guardian Tonbee is beaten down. Tsunade dispatches Team Yamato to escort the girl safely to the Tsuchigumo village. Naruto, Sai, and Yamato trail Utakata, who, once he learns they are not enemies, entrusts Hotaru to their care. Along the way the group discovers that a forbidden clan technique has been sealed into Hotaru's back, something she herself requested to honor her grandfather's dream of restoring the clan.

Utakata is revealed as a Kirigakure missing-nin accused of killing his own master, and a squad of Mist Anbu led by Tsurugi pursues him. A truce lets him stay with the team until Hotaru is safe. Meanwhile the mysterious Shiranami, secretly the Magaki leader, wins Hotaru's trust before abducting her back to her village, where he uses his own technique to seize control of the residents. Naruto and Utakata track him down and, with Team Yamato holding off the mob and the bandits, manage to rescue Hotaru.

Once Hotaru is safe, Team Yamato parts from the pair, and Utakata agrees to train the girl as they travel together. Before setting out, he goes to seek answers from the Mist Anbu about his late master, only to find their discarded masks and realize the unit has been killed. The Akatsuki's Pain then appears, announces his intent to seize the Six-Tails, and after a struggle captures Utakata.