AUTHOR'S NOTE!!!
Put simply, this is a prologue, a direct dialogue from KH II. I didn't write it (though I did correct some of the grammar) but it is necessary to explain the rest of the story.
(Xemnas starts to disappear; Mickey runs up and jumps into the portal after him)
Sora: He's gone...
(Sora slumps to the ground and slams his fist into it. Goofy puts a hand on his shoulder)
Donald: Sora, Goofy.
Goofy: What's goin' on?
Axel: Way to fall right into their trap.
(They see Axel leaning against a rock)
Axel: C'mon, it's a set-up by Organization XIII. Xemnas is using you to destroy the Heartless---that's his big master plan.
Donald: Xemnas?
Axel: The guy you just saw. He's their leader. Got it memorized? X-E-M, N-A-S.
Goofy: Organization XIII wants to get rid of the Heartless?
Axel: Man, you're slow.
(Axel points to the Key blade)
Axel: Every Heartless slain with that Key blade releases a captive heart. That is what the Organization is after.
Donald: So what are those guys gonna do with the hearts?
Axel: I'm not telling.
Donald: Tell us!
Sora: You...you're the one who kidnapped Kairi!
Axel: Bingo. The name's Axel. Got it memorized?
Sora: Where is Kairi?
(Axel scratches his head)
Sora: Please. Just tell me!
Axel: Look, about Kairi...I'm sorry.
Saïx: Axel!
(Saïx appears between Axel and Sora)
Axel: Uh-oh!
(Axel starts to vanish. Sora tries to run to him, but Saïx holds out his arms and stops him)
Saïx: We'll ensure he receives the maximum punishment.
(Axel is gone)