I believe Yozora is an inversion of Sora.
I'm curious, what are the implications of this for you? The fact that their names are inverted is fairly obvious, but what the intent behind such a move is much less clear. Are they meant to be enemies? Allies? Two people who occupy the same space in parallel universes?
No one really knows for sure about any of this stuff--all we can do is craft a theory and see what happens.
Yozora mentions in order to get to the Final World (or what appears to be a digital version of it) he had to go through trials. In order to unlock the Yozora boss battle, you have to finish the DLC and the limit cut episode and fight data versions of member of the True Organization XIII, which seems like a type of trial.
I don't know exactly how meta the game is going to get, but to be fair the "Sora" fighting the Org battles in Limit Cut is actually Riku controlling a digital Sora avatar, so I wouldn't count those as a trial Sora is actually going through himself. But if it is meant to be a meta thing about the player themselves then...fair enough.
I'd also like to hear some thoughts about how this ties in with Versus-XII and Final Fantasy XIII in general since i know nothing when it comes to Final Fantasy.
Nomura has stated several times now that whatever Verum Rex is, it isn't supposed to be Versus 13 in its entirety. Inspired by, of course--but I think it's more that he is taking certain ideas he really likes, recycling and re-purposing them in Kingdom Hearts colored wrapping paper. What concepts, exactly, that he is going to keep and what he is tossing is anyone's guess. From what I know about the Versus 13 concept, it was to be somewhat of an inversion of FF13's themes (hence, "versus" in the title). You can always read up on the plot of 13 on wiki, but from what I remember, the main theme of FF13 is about defying the fate given to you and carving your own destiny. It seems that Versus 13 was going to be about, conceptually, realizing what your destiny is meant to be and fulfilling it. Kingdom Hearts has always had a strange in between stance on the concept of destiny. At some points it makes it very clear that destiny cannot be unwritten. However, some of the events in 3 seem to suggest otherwise.
Another point I remember is that while FF13 involved the characters serving a Goddess of Life, the Versus 13 main cast were supposedly from a family that served the God of Death. I believe the main character, Versus' "Notcis" was meant to have eyes that could see the souls of the dead or recently deceased. There was also supposed to be some kind of "Unseen Realm" that was like the land of the dead and some part of the game I believe involved finding the door to this place.
Again, this is also speculative stuff since the game never actually released.
One concept that was meant to carry over between the two titles was the aspect of "crystalization", which we see in FF13 when a person fully completes a given task, they turn to crystal and fall into a suspended animation of sorts until they are awoken again. In the bad ending we see something eerily similar happen to Sora. However, it is interesting to note that the crystalization was, I believe, at the request of a God or the hand of destiny or what have you. The fact that Yozora can do it himself is interesting.
If anything, I think Nomura wants to more deeply explore the concepts of the land of the dead, the meaning of life/reality, and the concept of destiny and if it can be averted or not since these are all things that Versus 13 was likely to explore and he seems to be hinting towards now. Apply that to KH now however you will.
One other thing I wanted to point out was that we know at some point both Sora and Yozora lose their "Kairi" character. Where Sora was successful in saving his, Yozora presumably was not, and she for whatever reason ended up in Sora's universe, waiting for him to save her. If we assume that both Sora and Yozora are having somewhat mirrored experiences, this could mean that Yozora either defied the option to, or was not able to change fate by time jumping to bring his girlfriend back. This could maybe speak to a difference in their situations, or a difference in personality. However, due to the fact that we still aren't even sure who the "real" Yozora is, it's very hard to say. All we know is that the physical form that we saw and fought wasn't apparently what "Yozora" is actually supposed to look like, and his girlfriend explained that his "heart was replaced" so...at this point what Yozora really looks like and what he's like personality wise is also a bit of a mystery.
There are far too many theories and possibilities that I think the team was right when they said it would be nearly impossible to guess where they are going next.
I personally believe that Kingdom Hearts (and to some extent the Black Box) have been supporting and running various simulated contained universes. The KH universe we have seen so far and the Verum Rex universe are both two separate iterations. Normally untouchable to each other, they can cross at certain key places and points and somehow these two universes have done just that. I think the "true" universe is one that was lost a very long time ago and possibly a future goal of the series might be to fully restore everything back to its original state. Possibly the reason we have a character like Yozora who looks sort of like Riku with Sora's name is because whatever is making these various universes only has limited control over its ability to create unique data, or whatever it is is following some sort of script and all universes need certain characters in them to function. Who knows.
Personally I think with the Xehanort Saga being over, they are perhaps looking for a way to shake things up. Introducing alternate dimensions or separate universes where things are similar but different allows them to reuse certain properties in different ways without breaking any continuity (sort of like the Monstro world in DDD).
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