Nibi Nekomata

Nibi is one of the "bijuu", a tailed beast of the ancient world. Seeking a way to create a ninja with a large amount of chakra that would be an unstoppable machine, the Nibi was placed inside Hidden Cloud kunoichi Yugito. Nibi has been refered to as an "ikiryou" or living ghost.

Ichibi Shukaku

Shukaku is one of the "bijuu", a tailed beast of the ancient world. Seeking a way to create a ninja with a large amount of chakra that would be an unstoppable machine, the Kazekage had Shukaku imbued within his unborn son.

Yamato

"Yamato" as he was dubbed by Tsunade, was an elite ANBU who led Team Kakashi when Kakashi was fatigued from battle. Yamato led the team of Sai, Naruto and Sakura to the Grass Country. They were to meet Sasori's spy who was spying on Orochimaru.

Yuuhi Kurenai

A Jounin master, Kurenai is the leader of Team 8 (Hyuuga Hinata, Aburame Shino, Inuzuka Kiba). Near the series start, Kurenai attained the rank of Jounin. She is highly trained in Genjutsu illusion techniques.

Momochi Zabuza

A missing-nin from the Mist Country, Zabuza fled his country after he attempted to assassinate the Mizukage and take over the country. After arriving in the Wave Country, Zabuza reluctantly started working for a man named Gatô in order to make fast money and help his enterprises. Gatô wanted Zabuza to stop the construction of a bridge which posed a danger to his business.