Why can Naruto still use Rasenshuriken?


When Naruto first used Rasenshuriken against Kakuzu the effect was massive. He
destroyed two of Kakuzu's hearts, but there were a huge after effect to him.
If I'm not mistaken, Tsunade advised Kakashi to ask Naruto never to use the
technique again due to the huge risk. So why is Naruto still able to use the
technique and have no side effects after that battle? I may have missed out on
something.




Naruto only used this jutsu one time in normal form (against Kakuzu, and got
many side effects, like you said), the other times he was at [Sage
mode](http://naruto.wikia.com/wiki/Sage_Mode), at this state he didn't damage
himself.

According to [Naruto
Wiki](http://naruto.wikia.com/wiki/Wind_Release:_Rasenshuriken):

> Naruto later improved the Rasenshuriken with Sage Mode. This allows him to
> throw it at his opponents, and removes the threat of damaging himself with
> the technique.




Naruto only used this jutsu one time in normal form (against Kakuzu, and got
many side effects, like you said), the other times he was at [Sage
mode](http://naruto.wikia.com/wiki/Sage_Mode), at this state he didn't damage
himself.

According to [Naruto
Wiki](http://naruto.wikia.com/wiki/Wind_Release:_Rasenshuriken):

> Naruto later improved the Rasenshuriken with Sage Mode. This allows him to
> throw it at his opponents, and removes the threat of damaging himself with
> the technique.

