KINGDOM HEARTS is the story of a young boy named Sora. When he was little, a strange girl washed up on the beach of the Destiny Islands. The girl spent the rest of her life on the islands, and became best friends with Sora and his friend Riku. The girl’s name was Kairi.
When they got older, Riku began to question where Kairi really came from, and how she got to the islands in the first place. So he devised a plan to set out and get off the islands and explore any and all outside worlds other than his own. The three friends began constructing a raft and planned to use it to sail out to distant and unknown worlds.
The night before they planned to set sail, a storm formed above the islands. Riku gave himself up to the darkness in an effort to go the outside worlds, and when Sora tried to save him, the darkness almost swallowed him as well. But a bright light gleamed in the darkness, and when it cleared, Sora was the wielder of a weapon with mysterious powers: the Keyblade. It was a weapon capable of fighting the darkness.
The storm swallows the islands and transports Sora to Traverse Town. A brand new world somewhere far away from his home. He eventually encounters Leon, Yuffie, and Aerith, who explain the story behind the Heartless, a wise man named Ansem, and the Keyblade. Sora teams up with Donald and Goofy – two servants of Disney Castle who were sent by their king to find the wielder of a mysterious key and follow him at all costs.
Sora, Donald, and Goofy travel to many different worlds searching for Riku, Kairi, and the missing king. On their journeys they discover that each world has a Keyhole that acts as a gateway to its heart. The Heartless are trying to use these Keyholes to consume each world in darkness. Sora uses the power of the Keyblade to seal each Keyhole before the Heartless can claim anymore worlds.
Eventually Sora finds Riku and Kairi again, but they are not the same as they were on the night of the storm. Riku has allied himself with the Heartless to save Kairi who had lost her heart on the night of the storm. As it turns out, Kairi is one of seven princesses whose power can open the door to the heart of all worlds: Kingdom Hearts.
Riku, consumed with jealousy toward Sora and the Keyblade, plunges deeper into the darkness and gains the power to wield a Keyblade of his own – a Keyblade that has the power to unlock the true potential inside a person’s heart. Using this Keyblade Riku attempts to free Kairi’s heart, which is burried somewhere deep inside Sora’s. But Sora refuses to let Riku take her heart. Riku and Sora clash, and when Riku is defeated Sora releases Kairi’s heart from his own. Kairi wakes up, but in the process, Sora becomes a Heartless for a short while. The light inside Kairi’s heart returns Sora to his normal self.
Sora and the gang set out to confront Ansem, who had been using the power of darkness to control Riku so that he may gain access to Kingdom Hearts. In the end, Sora, Donald, and Goofy defeat Ansem, and with the help of Riku and King Mickey, they seal the Door to Darkness. Riku and the King were sealed inside the door while Sora, Donald, Goofy, and Kairi were left on the outside. Kairi was returned to the Destiny Islands while Sora, Donald, and Goofy continued on their journey to find Riku, the King, and the ever-elusive Door to the Light.