Finally, we're back to talking about story content.
It's actually pretty amazing that, after the original Kingdom Hearts, Kairi has a huge problem with almost completely ceasing to be relevant to the plot. Even though she spent most of the first game in a state of limbo, she still does contribute to the story in some ways.
In Kingdom Hearts 2, her only real contribution is being kidnapped, and then not being kidnapped anymore while Sora goes off and actually deals with the real plot. It gets worse from here on. At some point, you'd be hard-pressed to remember who Kairi is. I wish that they'd make more use of her. As it stands, she only serves as motivation for the real heroes, without taking any actions of her own.
Also, points to Sam for correctly figuring out the Xehanort/Ansem family tree on his first try.