[Skarn]

Ever since that chapter came out it's been confusing people...

There was an old thread about it that Schick made, but some new discussion would be nice too.

What is known is that apparently the kyuubi's chakra either already consisted of yin and yang parts, or it was split into such. And the yang half is definitely sealed into Naruto.

Where is the yin? That's a good question xD Some think it's with the "reaper" used for the reaper death seal technique. I think Schick said it probably could not be separated from the yang, and therefore was "dragged down with it" inside Naruto(meh, Schick could explain that better). Other than that, it could sealed into Minato's body...

Also, it could be that the yin half was sealed similar to the sanbi sealing method(into a scroll). This could be the "key" that Jiraiya had.

I have another theory, but I dunno, I'm still in the process of gathering information on that one. We'll have to see.