After triumphing over Ansem and bringing back peace to the world, Sora, Donald, and Goofy face a new quest as they search for their missing friends, Riku and King Mickey. Their journey leads them through the Castle of Oblivion where they cross paths with enigmatic foes, causing them to gradually forget their past. Amidst this memory loss, Sora grapples with the concept of cherished memories and must ultimately decide which path to follow.