I have played the game, and have beaten it. In the main story, you control Sora as you go through the floors of Castle Oblivion, and try to find Naminé, only to find out that she's a manipulator of memories. Along the way, you fight against the Riku Replica, Axel, and other members of the Organization, until you finally fight against Marluxia. After beating the game, you can experience the story from the perspective of Riku. This mode is called REVERSE/REBIRTH! In Riku's story, his only ally is The King (Mickey), and Riku's deck is already pre-built for each different world you go to. And Riku must fight against Ansem to clean out the darkness in Riku's heart. But Riku learns that not all Darkness is bad, but can be used for a greater good.
And in case you're all wondering how I put that "é" in the name, I just hold the Alt key, and press 0233 on the number pad. In short: é = Alt + 0233
