After closing Kingdom Hearts, Riku and the King are stuck within the world of Darkness, attempting to find the other group, Sora, Donald and Goofy. Riku's story is very similar to Sora's in the sense of how to battle, the places visited, and things like that. These differences are:
- Riku jumps higher than Sora.
- Riku's only attack card is Soul Eater, a Riku specific attack card.
- The amount of damage Riku deals is based upon his AP, or Attack Points.
- Riku's deck is closed for editing. Players may view his deck at anytime, but nothing past that.
- Riku automatically keeps all the boss card he obtained in his deck.
- Riku has an ability called Dark Mode. Riku will enter Dark Mode when enough DP, or Dark Points, have accumulated in battle. Dark Mode allows Riku to use sleights and increased movement and abilities.
- Riku's dodge now covers half the screen. In addition, he can now dodge up and down while in Dark Mode
- Pressing while in the air will result in a double jump, in which Riku zooms in on an enemy and lands behind it. Useful in dodging attacks.
- + while using two attack cards results in Riku spinning around with the Soul Eater, damaging all enemies around him and sending enemies upward. Pressing will let Riku continue to spin for a couple more times.
- Falcon Strike: ++Attack Card: Riku double jumps, zooms in on an enemy, and strikes it from the behind with the Soul Eater.
- Riku's second attack in a combo immediately follows up with a quick attack that stuns the enemy. Riku's third strike in a combo is where he jumps up in the air and attacks.
- Riku's only sleights are:
- Dark Break (only in Dark Mode)
- Dark Firaga (only in Dark Mode)
- Dark Aura (only in Dark Mode)
- MM Miracle
Riku is really a lot different from Sora. Most of these things are double-edged swords, but some are really good.
Riku starts the game not on a floor of Castle Oblivion, but on the 12th Basement of Castle Oblivion.