So I was thinking, yeah, Yamato has some control over the kyuubi because of the cells he 'inherited,' but what about Tsunade. She's the first's granddaughter. Shouldn't she have SOME control? This is just kinda outta the blue, but I'm reading the manga where the four-tails comes out, and I remembered that she was an heir.
Astute observation J-Man, but you're forgetting one crucial piece of evidence. Yamato cannot control the Kyuubi, he can only surpress its chakra. He can onl do this because he has the first's Kekkai Genkai. How the ability to create wood is related to the ability to surpress the chakra of the Kyuubi is beyond my reasoning. However, that aside, Tsunandehime has not shown herself to posses the first's Kekkai Genkai.
Actually, here's something interesting. The first could surpress the Kyuubis chakra because he could weild the power of nature itself. The Kyuubi, being called a 'natural' disaster may shed some light on why he can do this. What if he could not only manipulate nature, but it seems logical to me to think that if you're going to manipulate nature you must also manipulate nature's chakra. This being said, it leaves me wondering if the first wasn't a sage.
I think that Yamato has a weakened version of the Kekkai Genkai. Like a tape recording of a tape recoring, or a clone creating a clone, its just not as good as the original.
Let me also poner this a moment. Was it only the Kyuubi's chakra the first was able to surpress, or was it all of the bijuu? It would make far more sense to me if it was able to surpress the Bijuu, but if not, then why could he only surpress Kyuubi?
Upon examining this theory it doesn't make a whole lot of sense simply due to the fact that if Kyuubi was made up of natural chakra an that wh the first could controll it, the why ca Ma and Pa not fuse with Naruto? The answer seems far too simple to substantiate the theory: because he doesn't want them to. Why would he not want them too? Lets examine.
aif Ma and Pa were able to fuse with Naruto this would make him able to stay in sage mode indefinately. This would make him insanely powerful, much more so than Jiraya, because his sage mode is far more perfected. Perhaps Kyuubi wishes to keep Naruto weak so that he will continue to have to rely on him. This will keep Kyuubi useful, and keep his prospect of taking Naruto over a possibilty. If Naruto is that strong, Kyuubi never gets used again, and thus can never take Naruto over.
Another possibilty is that Kyuubi knows something about sage mode that we don't. Perhaps there is a risk to prolonged sage mode, or even the Ma/Pa Sage mode, and this may be the reason we never saw Jiraya use it until his fight with Pein. During his fight with Oorochimaru it would have been an excellent time to bust out Ma and Pa, but he chose not to, why?
Perhaps the longer one stays in sagemode the more likely that it is that the balance will become interrupted or distorted and the next thing you know you're a very ugly stone statue.
Of course the simple answer to all this is that Kishi simply hadn't thought up sage mode yet when the Sennin fight occurred. We never even hearof Sage Mode until Jirayas fight with Pein.
By the way, while I did enjoy the thought of Fat Pein going "green" I don't think this will happen. Two reasons why.
1. Jiraya trained Nagato AFTER he had become a sage. He may have even tried to teach Nagato the technique or simply tld him about it. In this way he would know the risk of too much nature Chakra.
2. Lets not forget tha Oorochimaru is a Sannin as well and was part of Akatsuki. If he didn't know about sages before then, Nagato could have learned from Oorochimaru about it.
In any case, wth these things I find it safer to assume that the villan knows rather than that he knows not.
That is all, for now.
How troublesome.