After reading Naruto chapter 604, there is only one question on most peoples' mind right now - Why did Kakashi kill Rin?
Of course there are already plenty of doubts about the whole thing, and with Madara and Zetsu involved that's no real surprise.
Anyway, this was the first chapter in a while that actually brought something to the table that felt fresh. Ever since the reveal of Tobi being Obito things have played out exactly as so many people predicted, and as such the chapters felt almost like they had been read before which meant they were rather boring. However, a lot of people have been curious about how Rin died, and so with this chapter we finally get to see something to care about again.
I personally don't believe for a second that Kakashi did that to Rin for any sinister reasons, and I have my doubts whether he actually did it at all. Madara has clearly wanted to use Obito from the start, but with Obito being so reluctant and constantly talking about his friends, it would come as no surprise if Madara used Zetsu to make something like this happen to make Obito easier to manipulate.
Don't get me wrong, if this had been pre-Kakashi Gaiden a case for Kakashi actually being responsible could have been made. We know back then he would have followed any rule laid out for him, and if killing Rin happened to be vital in a mission succeeding, he may well have done so. After Obito's words and his later death however, it was obvious Kakashi was a changed person, and killing Rin after the promise he made seems out of the question.
What with the way Obito's vision was impaired briefly when he felt the pain in his eye while on the way, it could very easily have been some kind of Genjutsu he was put under without him realising, and then of course the Kakashi and Rin thing would be perfect for breaking his spirit. Another theory I have heard is that it may be a couple of transformed Zetsu clones pretending to be Kakashi and Rin - Again this is more than possible, we know Obito needs a reason to turn down the wrong path, and for Zetsu setting up such a scenario would be extremely easy.
The only other thing that has been predicted is that maybe Rin was being controlled or just generally something forcing her to behave in a way that meant Kakashi had no choice but to kill her. I for one don't believe it, as it's a needlessly more difficult path for Kishi to go down, and the look of shock on Rin's face to me proved it can't be something she wanted or expected from Kakashi.
Overall this was a pretty good chapter, it finally broke away from the very predictable nature of the previous few chapters and finally we have some kind of talking point to go over as well.