An expanded re-release of the game featuring new and additional content, Kingdom Hearts Final Mix, was released exclusively in Japan in December 2002.

The Final Mix version of the game was later remastered in high definition and released globally as part of the Kingdom Hearts HD 1.5 Remix collection for the PlayStation 3.

It follows the adventures of Sora, a cheerful teenager who fights against the forces of darkness alongside his allies, including Donald Duck, Goofy and other Disney characters.

Kingdom Hearts is influenced by its parent franchise, Final Fantasy,[6] and carries gameplay elements over into its own action-based, hack and slash system.

[13] The game progresses linearly from one story event to the next, usually presented in cutscenes, though there are numerous side quests available that provide benefits to the characters.

Combat in Kingdom Hearts occurs in real time and involves pressing buttons to initiate attacks by the on-screen character.

The HP meter determines the character's health and reducing whenever they take damage, although it can be replenished by using healing items or spells.

The gameplay for piloting the vessel is different from the rest of the game, as it switches to a rail shooter format in which the player controls the Gummi Ship from a rear third-person perspective as it travels in an outer space setting.

Each Disney world is inhabited by characters from the film: including Hercules and Philoctetes in Olympus Coliseum, and Aladdin, Jasmine, and Jafar in Agrabah.

For most of the game, Sora is joined by Donald Duck and Goofy, who are a court wizard and captain of the royal guard respectively,[21] and were sent from Disney Castle to find the Keyblade.

[29][30] Sora later challenges Riku, stating that his heart derives strength from his friends, inspiring Donald and Goofy to return to him and allowing him to regain control of the Keyblade.

[14] The game began development in February 2000[38] and originally focused more on the gameplay with a simple story to appeal to Disney's target age range.

[41] Nomura included the teaser in order to gauge fan reaction to the possibility of a sequel; he felt that if the idea was unpopular, then it would be best to leave certain events in the game unexplained.

[48] While there are arranged melodies derived from previous Disney films, most of the soundtrack consists of original themes written specifically for the game by Shimomura.

[54] A special effort was made to preserve the official voice actors of characters from the Disney movies used in Kingdom Hearts, including Tony Anselmo, Bill Farmer, & Wayne Allwine as Donald Duck, Goofy, and Mickey Mouse, respectively.

Other actors who reprised their roles included Tony Goldwyn as Tarzan, James Woods as Hades, Jodi Benson as Ariel, Kathryn Beaumont as Alice and Wendy Darling, Scott Weinger as Aladdin, Linda Larkin as Princess Jasmine, Gilbert Gottfried as Iago, Pat Carroll as Ursula, John Fiedler as Piglet, Chris Sarandon as Jack Skellington, and Kenneth Mars as King Triton.

The English version featured Haley Joel Osment as Sora, David Gallagher as Riku, and Hayden Panettiere as Kairi.

[55][56] Other voice actors included Billy Zane as Ansem, Christy Carlson Romano as Yuffie, David Boreanaz as Leon, Sean Astin as Hercules, Lance Bass as Sephiroth, and Mandy Moore as Aerith.

[58] To help market the English release of the game, Square launched the official website in April 2002, which featured trailers, a "Name-In-Game" sweepstakes, and other Internet content.

[2][14] Other marketing efforts included auctions of the game and related items before the North American release[60] and a Consumer Demo Day in San Francisco, California.

[62] New scenes, clarifying certain plot points, such as Riku's journey and foreshadowing of Kingdom Hearts II, were included, but no new dialogue was recorded.

[62] The optional bosses first included in the English version were introduced to Japanese players for the first time, along with a new fight against "Unknown Man," in an attempt to raise interest for the sequel.

Other changes include new abilities, new weapons, new items, additional and recolored enemies,[64] and gameplay tweaks to make the game easier for the player, along with two new levels of difficulty.

A limited "Platinum Edition" version of Kingdom Hearts Final Mix was later released with an action figure of Sora, a sticker set, and sketches of some of the main characters.

[74] A piece of free downloadable content for the PS4 version released in June 2017 added a Theater mode for Kingdom Hearts Final Mix; this was included by default in later ports of the compilation.

[89] At the end of April 2003, Square announced that Kingdom Hearts had sold its millionth copy in the United States, which made it eligible for PlayStation's "Greatest Hits" status, and over 3.0 million worldwide.

GameSpot cited "tedious" gameplay and Gummi Ship sections as "pale imitations of the Star Fox series," but stated that the combat was fun, particularly the boss fights.

[125][126] Kingdom Hearts II is the third game in the series, set one year after Chain of Memories, and was released in Japan on December 22, 2005, for PlayStation 2.

[128] A Kingdom Hearts game was developed exclusively for V CAST, Verizon Wireless's broadband service, and was released on October 1, 2004, in Japan and on February 4, 2005, in the United States.

[132][133] The following title, Kingdom Hearts: Melody of Memory, set after the Re Mind scenario, was then released in Japan on November 11, 2020, and worldwide two days later.