Well...This is gonna be without any KHII related things...Because I don't know what's going to happen in the game...
The worlds of KH is separated by invicible walls. I believe that all of those worlds once were bound together as one great world, were people lived and were happy. They were blessed with a great Light, wich made them happy...and they loved it. But then they began to fight over the Light, because people didn't wanna share it with eachother, and thats how Darkness came to be.
In order to secure the world....The Light split the great world up into many small worlds, and inviceble walls were build by the Light to seperate the worlds...That was the only way for people to live in peace and not have wars against eachother. It became the World Order, wich couldn't be broken. And if it did...The worlds would once again be overrun by Darkness, and the Darkness had a great impact on the worlds duing the time of the wars...It too had secured it's own way, so the worlds could once again fall into Darkness. In every world, the Darkness had made a door, wich lead into the heart of the world, were darkness ruled. The door could only be opened by a person wich used the Darkness..Even if he didn't knew he did. All the doors lead to the very same place, were all the worlds hearts were. Kingdom Hearts. But the Light saw this coming, so it made sure that darkness wouldn't be the only ruler in Kingdom Hearts, so it made a little piece of the Light shine in there behind the Darkness. But to be sure, The Light made Keyholes in the doors. It also made a very special Key called the Keyblade. If the Darkness in peoples hearts should ever come again and open those doors, then the Light would choose a very special person to counter the Darkness. That person would recieve the Keyblade, and become the Knight of Light. He had to go to as many worlds as he could and lock the Keyholes wich is hidden in every world. The Darkness also created a Keyblade, The Keyblade of Darkness.
Because Kingdom Hearts both contained Darkness and Light, then both keyblades were needed to close the Door to Kingdom Hearts.
One could only hope, that the Light would choose a good person with a strong heart to wield it's Keyblade, and that the Darkness would choose wrong, and have a person with a good heart to wield the Keyblade of Darkness...
Well....That's how I see it...
