Yes, it is obvious. We already know chakra is "explosive". The only way we know of to make chakra balls is to compress and rotate it randomly, using the image training Jiraiya gave Naruto to control it. Chakra won't stay looking like a ball unless someone is compressing it. It will blow up, like it did in Naruto's mouth cannon when he stopped compressing it.Originally Posted by Killa-Eyez
We also already know that the Rasengan changes color depending on the size and amount of chakra used. Remember the purple Rasengan Naruto used against Stage II Sasuke?
Yamato and Orochimaru recognized the chakra balls as Rasengans. As Yamato explained, the Kyuubi's chakra was essentially spilling out of its container (Naruto) and trying to take the shape of the real Kyuubi. The fact that Naruto was able to
I didn't say that Naruto taught it to the Kyuubi. I said Naruto did the attack, using Kyuubi's chakra. Sure, it wasn't even exactly all Naruto, since his instincts were to become more like the Kyuubi. Obviously Naruto alone wouldn't have been able to pull of a Rasengan of that scale. And he might not have even thought of it without the Kyuubi's instincts. But it seems very clear to that they need each other to pull off that move.