Sora seeks out his friends, finding Riku, who disappears into darkness. At the same time, Sora obtains the Keyblade. The islands are destroyed, and Sora is left adrift. Meanwhile, King Mickey has left his world to deal with the increasing darkness and left instructions for mage Donald and knight Goofy to find the "key".
Donald and Goofy use a Gummi Ship to travel to Traverse Town, to where Sora has drifted. Sora encounters the shadow creatures again, and meets Leon, who explains the shadow creatures are Heartless, beings that consume hearts, and that the Keyblade is the only weapon capable of defeating them. A man named Ansem, the leader of Leon's home world, is said to have studied the Heartless. Sora meets Donald and Goofy and the three decide to travel together: Donald and Goofy to find Mickey, and Sora to find Kairi and Riku. The three go to various worlds based on Disney films, finding that the Keyblade also locks "Keyholes", passages the Heartless use to take the heart of a world. A group of Disney villains, led by Maleficent, seek out the seven Princesses of Heart to unlock the Keyhole that leads to Kingdom Hearts, a repository of knowledge and power and the source of all hearts. This group includes Riku, whom Maleficent promises she will help in finding Kairi. Maleficent sows distrust in Riku, telling him Sora has abandoned him and Kairi for new friends and the Keyblade. An increasingly antagonistic Riku finds Kairi's body, but cannot find her heart.