Soooo yeah.they're fighting and then BOOM. Then I think somehow the 4th is seperated from the 3. This is several years ago when they are kids, and the 4th is their sensei. Obito, Rin, and Kakashi, and the 4th Hokage are on a mission. i forget the whole story on it so its not very accurate
and he wanted to give him his eye as a present so he ripped out his eye and gave it to Kakashi so he has mangekyou sharingan. Kakashis friend was dying or something my buddy told me.