Although life on Destiny Islands is comfortable and easy, three friends—Sora, Riku, and Kairi—yearn to explore the many worlds beyond. One fateful night, their wish comes true sooner than expected when dark forces known as "Heartless" invade their island. Overwhelmed by these creatures, the islands are consumed by darkness, taking Riku and Kairi with them. However, before Sora succumbs to the darkness, a blade of light appears in his hands: the "Keyblade," which grants him the power to defeat the Heartless. Meanwhile, in the world of Disney, residents are in an uproar over the disappearance of their king, Mickey Mouse. Leaving only a note behind, Mickey explains that he has gone to investigate an imminent danger threatening all known worlds. Furthermore, he instructs his aides, Donald Duck and Goofy, to seek out the one carrying a "key"; the one who can save them from their crisis. Thus, the pair sets off on their search, with the first stop being Traverse Town. Sora awakens in that very same town, only to find it plagued by the Heartless. Although finding his friends is his main concern, as the wielder of the Keyblade, he must accept the grand fate thrust upon him; many more worlds have come under attack, and he and the Keyblade are the only hope of liberating them.