3 more months
~ 1.5 years
Rereading chapter 673 and I have this question to ask:
When naruto makes his fuuton: rasenshuriken, the wind element is what makes it fly through the air right? If so, how was naruto able to make his Senpou Youton: Rasenshuriken fly through the air without the wind element?
That makes me remember...
Didn't Tsunade told him not to use his RasenShuriken, because he was destroying his arm to the cellular level everytime he used it?
She said that if he continued to use it, he might become unable to mold chakra in his arm.
How did he fix that issue? Sure, he's throwing it now, but he is still holding it in his hand before he can throw it.
Or did Kishi simply forgot about it?
The impact was what was hurting Naruto's hand, not the jutsu itself. Notice how the RasenShuriken expands when it hits Kakuzu and involves Naruto or parts of Naruto in its field of attack. Throwing it removed that weakness, and so did Kyuubi's chakra defense, so Naruto can use it without getting hurt. Making and holding the RasenShuriken doesn't hurt him.
Then there's also Sage Mode with which he doesn't really need tot throw it.