Ok heres the deal(Spoilers ahead!):
Sora lives on this island with his bestest friends in the world!
And he lives with Wakka and Tidus from FF and that other chick that I forget.
Anyways Sora along withe his friends Kairi and Riku are planning to visit other worlds so they are trying to build a raft.
So you spend the first half hour of the game building and finding food for your raft.
And one night a storm comes and Sora is worried about the raft so he stupily goes out into a LIGHTNING STORM and is surounded by heartless( the bad guys... duh.) To be continued!