Kingdom Hearts Story
Kingdom Hearts begins on the lush, tropical islands called "Destiny Islands", home to the main characters Sora, Riku, and Kairi. The three children wish to leave the islands that they have been confined to all their life, so they build a raft to escape. The night before the voyage, a storm sweeps through the island, and evil shadow-creatures called the Heartless appear. The three friends are separated. When Sora finds Riku surrounded by darkness, Riku disappears and Sora has to fight the Heartless, who are being used to tear down the walls between worlds. After the battle, Sora receives his weapon, the mystical Keyblade, and sets out to defeat the Heartless and be reunited with his friends.
From the Destiny Islands, Sora lands in Traverse Town, where he joins Goofy and Donald Duck in their quest to find King Mickey Mouse and defeat the Heartless. In their adventure, the trio explore many Disney-themed worlds, including Aladdin's Agrabah and The Little Mermaid's Atlantica. Along their way, they lock "keyholes" to the heart of those worlds, preventing the Heartless from consuming their worlds. Standing in their way, however, is a cabal of Disney villains, with Maleficent as their leader and Riku as her apprentice. Seeing Sora as apathetic towards Kairi's fate, Riku has taken responsibility into his hands and struck a deal with Maleficent, in order to help Kairi regain her heart. The goal of Maleficent and her group is to collect seven maidens of the purest heart, the "Princesses of Heart", in order to open the pathway to Kingdom Hearts, which is supposedly a repository of power and knowledge Maleficent intends to use in her plan to rule all worlds.
Finally reaching Hollow Bastion, Maleficent's headquarters, Sora confronts Riku directly, ending with the revelation that Riku is also a Keyblade master and through the loss of Sora's own Keyblade. Unfettered by the loss of his weapon, Sora puts his faith into his friends and thus wins back the Keyblade, sending Riku to run off and lick his wounds. It is during this time that a mysterious being offers him greater power with which he could use to defeat Sora. Riku impulsively accepts. Sora and his teammates face and defeat Maleficent, allowing a strangely-behaved Riku to strike her with a unique type of Keyblade, one that opens hearts. This transformed Maleficent into a dragon that reflected the darkness in her heart. Sora's party meets and exceeds the challenge, destroying Maleficent.
Sora confronts Riku again. Only, this time, it is not truly Riku; it is actually Ansem, the scientist who was researching Heartless, occupying Riku's body. Ansem desires to become part of what he believes to be the primordial phase of existence, the darkness that he believes to compose Kingdom Hearts. Kairi is revealed to be a Princess of Heart, and her heart was trapped in Sora's body ever since they got separated. Sora and Ansem battle, with Sora as the victor. In order to free Kairi's heart, Sora impales himself on Ansem's Keyblade, losing his own heart while restoring Kairi and freeing the other Princesses' hearts, as the Keyblade was composed of their hearts. However, the pathway to Kingdom Hearts was opened.
Now a Heartless, Sora scampered to Kairi's protection. Knowing that it was truly Sora, Kairi's light pulled him from the infinite darkness and restores Sora. They flee Hollow Bastion in face of the immense number of Heartless pouring through the pathway to Kingdom Hearts. They return to lock the keyhole and later travel to Kingdom Hearts itself, facing Ansem in a climactic final battle.
Though the light of Kingdom Hearts defeated Ansem, the door threatens to unleash millions upon millions of Heartless onto the universe. Sora, Donald and Goofy attempt to close the door, but their strength is not enough. Riku, who has regained his body, helps the others close the door on the other side, along with King Mickey Mouse. Using his own Keyblade, Mickey locks Kingdom Hearts from the inside, but this forces himself and Riku to stay inside. Before the door is locked, Riku tells Sora to take care of Kairi. Sora and Kairi's reunion is cut extremely short as they are pulled apart by the reforming Destiny Islands. Sora promises to return to Kairi once he finds a way to bring Riku out of Kingdom Hearts.