Obito Uchiha

appears in the Kakashi Gaiden arc as a former teammate of Kakashi Hatake and a member of Team Minato.

Background
Obito graduated from the Ninja Academy at the age of 9, and got promoted to Chunin at the age of 11. During the Third Great Shinobi War, Team Minato is assigned to destroy the Kannabi Bridge. Because Kakashi has recently been promoted to Jonin, he is to be left in charge of the mission. Before setting out, however, Minato and Rin give Kakashi gifts, something Obito forgot to do. Minato leaves them to go fight on the front lines, and Rin is soon captured by Iwagakure forces. Kakashi chose not to go save her, placing the mission's completion first, but Obito refuses to comply, stating that while those who break the rules are trash, those who abandon their friends are worse than trash. They part ways.

When Obito finds where Rin is being held, he is immediately attacked by Taiseki. Kakashi, having had a change of heart, arrives in time to save Obito and Taiseki uses the Hiding Camouflage Technique to disappear. Invisible, Taiseki is able to damage Kakashi's left eye. To save his teammate Obito awakens his Sharingan, immediately proving proficient enough with it to locate and kill Taiseki. Obito and Kakashi go to save Rin, but once she is freed an enemy-induced cave-in starts. Obito pushes Kakashi out of the way of a falling rock and his right side is crushed. Unable to free himself, Obito asks Rin to give Kakashi his remaining Sharingan eye to make up for not giving him a gift earlier. Once the eye transfer procedure is complete Rin and Kakashi are forced to leave, the cave continuing to collapse around them. Obito dies thinking of them both.

Personality
Obito had a chronic tardiness, something Minato attributed to his frequently performing random good deeds. This loose treatment of rules caused him to have a rough relationship with Kakashi. While Kakashi believed that the rules were everything during his time with Obito, whereas Obito believed that self-control and caring for one's friends was more important. Despite his carefree appearance, Obito often suffered from self-doubt, as while he boasted that he would surpass Kakashi once his Sharingan awakened, he later stated that he saw himself as a "washout" among the Uchiha. Obito had romantic feelings for Rin, but never was able to confess them to her. Many of these personality traits are adopted by Kakashi after Obito's death.

Despite the fact that he is an Uchiha like Sasuke, with the Sharingan and fire-style ninjutsu, Obito is much more like Naruto, particularly in personality; both were at first goof balls desperate to get attention, they look similar, and try to best their rival teammates (Kakashi and Sasuke, respectively). Both of them also had a crush on their female teammate (Rin and Sakura), who each preferred the other teammate (Kakashi and Sasuke) instead.

Trivia

 * Although he has yet to make an actual appearance in the anime, he is seen in a picture twice. The first time his goggles are colorless, and the second time they have a faint orange-tint like they do in color illustrations from the manga.
 * Before Tobi was revealed to be Madara Uchiha, several fans hypothesized that he was Obito Uchiha, as his only shown eye was the opposite of the eye that was inserted in Kakashi. They also have similar personalities, hair styles, as well as the same blood type, "O". The spelling of Obito was also similar to Tobi, creating the fan reference of ObiTobi, or Tobito. Even though Tobi has been referred to as Madara several times in the series, some fans still insist that Obito is somehow connected to Tobi or Madara.