Finally registered after reading for years just because I had to mention this, since it hasn't been brought up. Everyone keeps mentioning Yamato. Did no one else catch this:

Attachment 132

Maybe it is in the translation, but the way the sentence is formatted and Kakashi is also speaking while looking directly at <whoever it really is behind him> really makes me think this isn't Yamato. Kakashi is even acknowledged with a nod back and the way "Yamato" looks in this scene even has the demeanor of Jiraiya. I would have expected something like, "How the hell did Jiraiya-sama teach this kid a technique like Rasengan? Unbelievable..." if he wasn't speaking TO Jiraiya. If it is Jiraiya, this brings up all kinds of weird questions.