Sora, Donald, and Goofy set out to find Riku and King Mickey, who vanished after sealing the door to Kingdom Hearts, and their search leads them to Castle Oblivion, a fortress where memories can be built, rewritten, or erased at will. Sora climbs the castle floor by floor as members of the mysterious Organization XIII, including Marluxia and Vexen, use his own memories against him. This manga adapts the video game of the same name.