Quote Originally Posted by AssertnFailure
Kakashi said his rasengan couldn't evolve any further because his chakra element form isn't compatible with the chakra manipulation. This implies that, regardless of skill, there's still a limit to a ninja's abilities. The impression I had was that the 4th's element form wasn't compatible with rasengan as well. In other words, perhaps only wind users can complete the rasengan. Does this mean asuma could perfect the rasengan? If he had the training and talent that kakashi has, then chances are, probably.
Interesting point. That is what i thought too since rasengan look like a small typoon or tornado. Maybe it goes well with wind. However, isn't Kakashi know how to make wind too? he said most of jounin can control at least 2 nature isn't it? and he has the sharingan that can copy or ther jutsu too.