Sora

Sora is a monk in the Naruto Series.

Background
Not much is known about his childhood, only that one day he went beserk and wrecked the Temple of Fire, a place otherwise believed to be an undestructable fortress. Afterwards he was loathed by some of the monks of the temple, and soon began recieving the same treament as a Jinchuriki. He wanted to become part of the Twelve Ninja Guardians. He hates himself because of his powers and gets angry when people stare at him. When they first meet he hates Naruto but then they become friends. Sora does not like getting help from people, especially ninja. He did not even want Team Yamato to come.

Filler Arc
Earlier in the arc, Sora fought Naruto Uzumaki because he thought Naruto was robbing a ninja's secret tomb. It turns out that Naruto is quite jealous of him and thinks that he doesn't need Sora's help. Later, when Naruto's chakra was being drained it appeared that when all of Naruto's chakra was gone and the demon fox started getting pulled that the demon fox himself called to Sora for help or warned him that Naruto was in danger.

Abilities
Sora is a wind natured chakra user like Naruto. He has special powers with wind. Sora is a monk in training who fought Naruto because he thought Naruto was robbing a ninja's secret tomb. His jutsu are wind style killer slash. Like Asuma Sarutobi, he has a special wind style weapon called the death claw. He works very hard in his training and he uses special Taijutsu arts only known to monks. His wind will cut anything, even chakra.
 * Element: Wind

Unconfirmed theorie
It seems that Sora is a jinchuuriki (and therefore hosts a tailed-beast). Throughout the series there have been some hints pointing in that direction: Asuma notes that Sora has a lot of chakra (like Naruto), The Kyuubi was able to call Sora and Tsunade refers to an event that happened when Sora was young. The firetemple got wrecked and the monks mentioned an "evil chakra" coming from Sora.

Trivia

 * Sora is introduced as the first filler character in Naruto: Shippūden thus doesn't make an appearance in the manga.