Obito Uchiha

Obito Uchiha was one of Kakashi's teammates in the manga exclusive Kakashi Gaiden.

Part in the story
Obito was a 13-year old Chunin in Team Minato with Kakashi, Rin and of course, Minato Namikaze (he wasn't Hokage yet). He's very similar to Naruto Uzumaki, goofy and desperate to prove he is a worthy ninja, mostly unrespected by peers and teachers alike. However, he is ready to put his life on the line for his teammates without hesitation. Obito carries the blood of the Uchiha Clan and has the power of the Sharingan within him.

Kakashi saved his life, but when they were fighting with a Rock ninja, Obito saved Kakashi's life as well, which caused him to be hit by a torrent of falling rocks. The whole right side of his body was crushed, slowly killing him. When Kakashi went to his fallen teammate's side, however, in confirmation of their friendship and as a gift for Kakashi gaining Jonin rank (Obito was the only member of the team not to have given Kakashi a gift), Obito gave Kakashi his left eye, and the Sharingan with it.

Although believed to be dead, it is possible that the Akatsuki member Tobi is actually Obito Uchiha, rescued from death (most likely by another member). There has been many arguments that Tobi is Madara Uchiha, but the manga states that Tobi only "has the power of Madara Uchia" not that he actually is Madara.

Personality
Kakashi's trend of being late comes from Obito. Obito was almost always late, and was carefree about rules, leading to a rough relationship between himself and Kakashi.

Appearance
Obito wore a ski mask-like pair of goggles with a see-through orange tint. He also wore dark blue pants and a jacket. His hair was spiky like Naruto's, and was a black color.

Trivia

 * Obito graduated from the Academy at the age of 9, he also got promoted to Chunin at the age of 11.
 * Kakashi's famous quote: "Those who break the rules are scum, but those who don't help a comrade in need are worse than scum." (English dub version) was actually Obito's original quote.
 * Kakashi's always late because he spends too much time honoring Obito after the Uchiha died.
 * When asked why he should have waken up earlier to honor Obito (thus getting more time to do important information) by Yugao Uzuki, Kakashi replied that he does.
 * Kakashi's Sharingan came from Obito, transferred through surgery performed by Rin.