Kakashi got his sharingon from Obito, who was trained by the fourth hokage with Rin and Kakashi. Kakashi got his sharingon on an ambu mission when an enemy ninja sliced his eye out. Then Obito was hit by an enemy ninja's earth style jutsu and crushed by a bulder. He then gave Kakashi his left eye. Obito was thought to have died there but he didn't. He actualy joined the akatsuki and changed his name to Tobi.