Quote Originally Posted by Abdula
I seem to vaguely remember something like that being mentioned. Wouldn't it be wonderful if Naruto suddenly got a metal boast, not really. Anyway it is a good point but the does not unseal the other part of Naruto chakra. Naruto has the Kyuubi's yang chakra, Jiraiya used the key to loosen the seal so Naruto can now access up to four tails, the key would only release the rest of the nine tails yang chakra. That is what I got from what Jiraiya said, there is nothing to indicate that Naruto will get the ying chakra that the fourth sealed. I have no idea how he would be able to get it back from the shinigami because I was under the impression that once something was sealed with the shinigami it was trapped for good, at least that is what I got from the third's battle with Orochimaru.
If you mean mental boost, then no thats not what I was referring to. I was referring to negative effects it would have on Naruto which could be a reason why it was sealed away in the first place.