Board Thread:Versus Debates/@comment-2245550-20160522071949/@comment-9782468-20160523024435

@X29, the SHaringan doesn't copy the technique, it takes in evry detail possible. The technique can only be copied by the Sharingan user if they already have the skill to use it. For example, Sasuke had to train to copy Lee's style because he wasn't physically up for it at first.

It's for this reason that Kakashi can't copy the Rasenshuriken. It's beyond his abilities, even if he sees it through the Rasenshuriken