Kingdom Hearts is a series of crossover action role-playing games. The series centers on the main character Sora and his search for his friends and encounters with Disney, Final Fantasy, and The World Ends With You characters on their worlds.

The series starts with Kingdom Hearts showing how a young boy named Sora is separated from his friends Riku and Kairi when their world, Destiny Islands, is invaded by creatures known as the Heartless. During the invasion, Sora obtains a weapon called the Keyblade that allows him to fight the Heartless. He soon arrives in another world, Traverse Town, where he meets Donald Duck and Goofy, two emissaries from Disney Castle sent by King Mickey to find the wielder of the Keyblade. The three band together and travel to different Disney-themed worlds, sealing the hearts of the worlds to prevent more Heartless invasions, and to find Riku and Kairi. Along the way, they encounter a group of Disney villains led by Maleficent, who are controlling the Heartless to capture seven maidens called the "Princesses of Heart", and use their power to open the door to "Kingdom Hearts" and rule over all the worlds.Though they eventually defeat Maleficent, the three discover that Ansem (Xehanort's Heartless) who has been controlling Riku's body, using Maleficent and plans to attain eternal darkness by opening Kingdom Hearts himself. Sora, Donald, and Goofy defeat Ansem and seal the door to Kingdom Hearts with the help of Riku and King Mickey on the other side of the door. Kairi remains back home to await her friends' return.