Kingdom Hearts 358/Secondhand impressions
According to IGN's Jeff Haynes, the trailer introduces "an additional 14th member (of Organization XIII) who happened to be female that resembled Kairi." The trailer shows single- and multiplayer gameplay including multiple Organization members.
And if the trailer impressions aren't enough, Haynes even played the game. Apparently, the computer-controlled partner in single-player is actually capable for once: "In many cases, he would land two or three strikes before we had a chance to, which was particularly useful when we were surrounded."