One of my favorite RPGs eva.
The basic storyline of the game is as follows.
You are a kid named Sora stranded on an island with his two friends, Riku and Kairi. You and your friends want to sail away from the island and escape. So you spend a few days gathering supplies, and on the night before you set sail, a storm hits. Then these little black creatures start appearing and attacking. You make your way to a little island connected to the main island by a wooden bridge and see Riku standing there with what looks like an orb of darkness. He says "Im not afraid of the darkness." and the orb consumes him. Then, some sort of blade in the shape of a key appears in your hand, and you start fighting the creatures. As you make your way back to the shore, a rather large creature appears, and you have to fight it. Once you defeat it, you appear in a strange town by your self. After exploring, you find Donald and Goofy and battle an armored heartless(cause that is what they are called). Then, they tell you that they are searching for their King, and that there are other worlds out there. So Sora joins them, hoping to find Riku and Kairi.
Overall, AWESOME!