The Kingdom Hearts video game series, developed by Square Enix in collaboration with Disney, is set in a universe consisting of numerous self-contained worlds based on intellectual properties from both companies. Many of these worlds are based on animated Disney movies, though Kingdom Hearts II introduced worlds based on live-action Disney films as well. In addition to the Disney worlds, a number of original worlds appear over the course of the series.
The series centers on the character Sora, a boy who searches for his lost friends and encounters Disney and Final Fantasy characters as he travels between worlds. In the first game, Kingdom Hearts, Sora fights against the villains of the series known as the Heartless and seals each world he visits to prevent their return. In Kingdom Hearts II, Sora helps the residents of these worlds again in search of his friend Riku. The Kingdom Hearts games have been both critically acclaimed and commercially successful and the design of the worlds has been praised for its faithfulness to the source material.