When Sora’s house is struck by lightning during a violent storm, his entire world comes crashing down around him, and he becomes separated from his two closest friends. The storm disperses the three individuals to different realms. Concurrently, upheaval can be heard coming from inside the Disney Castle. King Mickey has gone missing, and Donald, the Court Wizard, and Goofy, Captain of the Guard, are on the hunt for him. During their travels, they come across Sora, who is also looking for his friends who went missing. It is explained to the three that the Heartless, which are terrifying monsters that lack hearts and originate from a dimension that no one knows about, are the ones to blame for the destructive storm.
Enticed by the strength of darkness, the Disney villains convince it to assist them in gathering the princesses of heart who are required to open a mysterious final door. This is accomplished by manipulating darkness itself. Sora, Donald, and Goofy form an alliance after uncovering a connection between the Heartless, the storm, and the disappearance of King Mickey. With their newfound allies, they assist well-known Disney characters in defending their worlds against the Heartless.
Players of Kingdom Hearts assume the role of Sora, the key blade wielder, and put themselves in his very enormous shoes. Sora is able to launch attacks with the blade, and as he levels up, he will unlock other attacks that can be linked together automatically. Both learning magic and putting healing things into a quick menu, which can only be used in real time, are abilities that Sora possesses. Sora will be accompanied on his journey by Donald and Goofy, in addition to a third character who is unique to each world or Disney film. Their artificial intelligence and equipment can both be customized, but they cannot be controlled directly. Many different sorts of objects, including raw materials for synthesis, will drop from defeated opponents. These can be repurposed by Sora by bringing them to the Synthesis shop in Twilight Town. There, they can be transformed into various useful goods, accessories, and weapons.
Flying through space in a Gummi Ship is required in order for Sora and his friends to get from one world to the next. It is possible to totally personalize the Gummi Ship, from its speed and armor to its armaments and its design, by piecing together components salvaged from damaged Gummi Ships, discovered in worlds, or purchased from a shop. As the player continues through the game, they will be able to construct ships that are larger and more complicated. Plans for these ships can be obtained from defeated foes or from an NPC that can automatically construct a Gummi Ship according to the player’s specified preferences.