well in the end it says it began with birth by sleep. which is what sora was doing at the beginning of the game. maybe there were evil keyblade wielders and good keyblade wielders because in the beginning it says one legend said that the keyblade wielder saved the world and another legend said it brought chaos and ruin upon it. also maybe someone is wondering what it is because it says that "i must know what this keyblade is. a key opens doors." and the guy walking in at the end is the keyblade master.