Ignoring the hentai above, hello all. This is my first post, but I've been a Naruto fan since 2005, and have been checking out this forum for a few weeks. Anyways, I think this is a crazy chapter, maybe even more so than the Tobito reveal. I think there's something more to this, which seems to be the general consensus.
I don't think that it's a genjutsu, it would be crazy if such an old Madara can have an effect on a battle so far away.
Zetsu seems improbable too, since Kakashi's clearly crying.
The traitor theory would work if it weren't for Obito's death, since Kakashi trying to keep his promise, would at the very least capture her, not kill.
Mangekyo activation wouldn't work either since Kakashi isn't a heartless bastard.
The last theory I've heard that doesn't make sense is that they were surrounded and Kakashi killed her to save Konoha secrets. Kakashi would give his life before doing that, because of his promise to Obito.
The only one that kind of makes sense is the accidental fog kill, where he couldn't see and accidentally killed her, but that still doesn't seem right. Rin, being a medic-nin, wouldn't be near the line-of-fire, I'd think. Kakashi would also be much more careful, since he's already experienced a teammate's death, and that would cause anyone to think twice before any move.