Xion doesn't know who she is. She doesn't know if she exists, she doesn't know where she's from, she doesn't even know her real name. There is an emptiness in her chest and in her head -- where there is no heart and there are no memories. Even when she is with them, her friends, there is still only emptiness.

Then Xion meets Kairi, and it all floods into her. There is a fullness in her chest and in her head, where there is a heart and there are memories.

They aren't Xion's.

But Kairi doesn't mind letting her live.