Board Thread:Naruto Discussions/@comment-4271790-20141016102132/@comment-1512913-20141019210408

Both Obito's soul and chakra entered Kakashi. Obito explained that chakra connects both worlds, as his soul used Kamui inside of limbo/purgatory world to return back to the impure land and "possess" Kakashi. His corpse shouldn't have had any chakra left of course, considering it was turned to ashes, but plot no jutsu whatever.