A few tidbits of information have been released on the upcoming PSP and DS versions of Kingdom Hearts. Three keyblade apprentice characters by the names of Ventus, Terra and Aqua will each have independent scenarios in the PSP version, Kingdom Hearts: Birth by Sleep, a prequel to Kingdom Hearts. The DS version, Kingdom Hearts: 358/2 Days, a story following the character of Roxas during Sora’s slumber between Chain of Memories and Kingdom Hearts 2, introduces Xion, the mysterious fourteenth member of Organization XIII and female keyblade wielder.
Source: The Magic Box