How did Kakashi get his scar?

Answer 1

Kakashi got the scar on his left eye when he was about the same age as Naruto, Sasuke and Sakura when the three first became a 3-man cell. In the manga(the anime may differ), Kakashi and two other people named Rin and Obito were a three-man cell. A guy named Minato Namikaze was the cell leader. There was a war going on at the time, and Minato was ordered to go on a mission with his cell to help turn the tide of the war in Konoha's favor. Unfortunately, along the way, Rin gets kidnapped by some enemy ninja. Kakashi says that they must leave her and complete the mission (he says that because when his father decided to save his friends he abandoned the mission, was disgraced and committed suicide. Kakashi lived by-the-book ever since). Obito says that that would be wrong and goes into detail why you should always help your friends and blah blah blah. Kakashi decides to help save Rin, but when he and Obito were facing one of the enemy ninja, the ninja snuck up on Obito. Kakashi protected Obito, but at the cost of his left eye. (thus the scar) Obito later has the right side of his body crushed by a cave-in when he pushed Kakashi out of danger. Obito tells Rin(who was a medical ninja) to give his remaining sharingan eye to Kakashi and then Obito died. (thus kakashi's single sharingan eye)