Sora and his friends, Riku and Kairi, plan on leaving their homes on Destiny Islands to explore their world, but their plans are interrupted when their world is attacked by the Heartless; monsters who steal people's hearts. During the attack, Sora wields a weapon called a Keyblade. Their world is destroyed, and Sora, Riku and Kairi end up on different worlds. Sora accompanies Donald Duck and Goofy to find his lost friends, and they travel to worlds based on different Disney movies, including "Alice in Wonderland", "The Little Mermaid" and "The Nightmare Before Christmas". Sora learns later that Riku has sided with Darkness and kidnapped Kairi. Riku is possessed by a Heartless called Ansem, who wants to capture seven Princesses of Heart so he can open Kingdom Hearts, the heart of all worlds. Sora rescues Kairi and Riku and defeats Ansem. Kairi goes home to Destiny Islands, but Riku stays in Kingdom Hearts with King Mickey to defend it. Kingdom Hearts then disappears. Sora tells Kairi he will not come home until he finds Riku, and leaves with Donald and Goofy to start a new adventure.