Kingdom Hearts: Chain of Memories is an action role-playing video game that was developed by Square Enix and Jupiter, and published by Square Enix in collaboration with Disney Interactive in 2004 for the Game Boy Advance (GBA). The game, which is an intermediary between the two larger-scale PlayStation 2 games in the Kingdom Hearts series, was one of the first GBA games to incorporate full motion video (FMV).

Kingdom Hearts: Chain of Memories is the second game in the Kingdom Hearts series. It is a direct sequel to Kingdom Hearts whose ending is set about a year before the events of Kingdom Hearts II. Kingdom Hearts: Chain of Memories follows Sora and his friends as they explore the mysterious Castle Oblivion while battling the sinister Organization XIII, a new group of antagonists in the series. The game introduces new characters and plot lines that further expand the Kingdom Hearts universe and set up the premise of Kingdom Hearts II. The game uses a new card-based battle system rather than its predecessor's real-time combat system.

Though it was not as successful as the other Kingdom Hearts games, Kingdom Hearts: Chain of Memories received positive reviews and sold well. It was praised for its story, graphics, and full-motion videos (FMV) but its card-based battle system was criticized. When it debuted in Japan, the game sold over 100,000 units in 48 hours. Kingdom Hearts: Chain of Memories was remade for the PlayStation 2 as Kingdom Hearts Re:Chain of Memories, which was packaged with Kingdom Hearts II Final Mix and released in Japan in March 2007. The remake was released in North America on December 2, 2008, and was remastered in high definition (HD) and included in the Kingdom Hearts HD 1.5 Remix collection, which was released in 2013 for the PlayStation 3 (PS3), and later for PlayStation 4 (PS4), Xbox One, and personal computer (PC).

Kingdom Hearts: Chain of Memories is a combination of a role-playing video game and a collectible card game. There is an experience point system that can be used to increase the character's maximum health and Card Points, or to learn new skills. The cards are used in the progression of the story and in combat. The game features a world map and a battle screen. The world map is an isometric area where the player traverses rooms. Enemies inhabit the world and track the player to engage in combat, which is initiated when the player and an enemy come into contact. Once in combat, the game switches to the battle screen, which uses the card-based battle system.

To advance through the game, the player uses map cards they obtain after winning battles to create rooms through "room synthesis". The map card the player chooses determines the properties of each room―including the quality of items and the strength of enemies. The color of each card has a specific effect: red cards affect the number and type of enemies; green cards affect the power of the player's deck; and blue cards affect the properties of the room, such as the allowance of treasure chests or the appearance of save points.

The game has three modes; two are story modes featuring Sora and Riku, and the third is a two-player battle mode. Initially, only Sora's story mode is available; once that story is completed, the "Reverse/Rebirth" mode becomes available. Reverse/Rebirth allows the player to play the second story mode featuring Riku and the battle mode in which two players using a Game Link Cable can battle each other.

Chain of Memories uses a real-time card-based battle system. The player can jump and maneuver around the battle screen as they do on the world map, but playing cards activate all attacks and other actions. Cards are ranked from zero to nine, and are can be used to make attack combinations (combos) or to break enemy cards. Card points (CP) are required to place cards in the player's deck; except for zero-ranked cards, high-ranking cards cost more CP than low-ranking cards. The player's CP, which is increased by leveling up, limits the number of cards the player can use in a deck. Breaking an opponent's card will cancel that attack and briifly stun the character. Zero-ranked cards can break any opposing card or combo if they are played after the opposing card or combo, but can be broken by any card or combo. Special enemy cards can be obtained by defeating enemies and bosses; these give the player temporary abilities such as enhanced offensive and defensive capabilities, or the ability to modify the attributes of certain cards.

Combo attarcks are created by combining cards in sets of three. These attacks are usually more difficult to break because the rank of the combo is the sum of the three cards in the combo. Some card combinations create a "sleight", a special combination that creates either a powerful physical attack, a magical spell, or a summon attack. After a card combo is played, the first card in the combo becomes unusable until the end of combat. The deck must be reloaded when the player runs out of cards.

Sora's and Riku's stories have some differences in gameplay. In Sora's story, Sora obtains cards by defeating enemies or by purchasing them at Moogle shops. In some cases, Sora must unlock specific cards through plot events before they become available. Sora can create and store three decks in the pause menu. Riku has a closed deck that cannot be customized and the cards in his deck change depending on the world he occupies. Riku is limited to mainly physical attacks, enemy cards, and Mickey Mouse ally cards. Riku can activate "dark mode" and unlock his sleight attacks if he accumulates enough "dark points", which are earned by breaking enemy cards and combos. The difference between Riku's card or combo and the enemy's card or combo is the number of dark points Riku will accumulate for that card break.

Kingdom Hearts chronology
Kingdom Hearts χ Birth by Sleep A Fragmentary Passage Kingdom Hearts Chain of Memories 358/2 Days Kingdom Hearts II Coded Dream Drop Distance Kingdom Hearts III Melody of Memory Kingdom Hearts IV
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Kingdom Hearts: Chain of Memories takes place immediately after the events of the first game. It is set in Castle Oblivion, a mysterious castle kept by Lord Marluxia. Sora and his teammates are told that the castle causes visitors to lose their memories upon entering. The lobby and areas between floors have a flower-theme while each floor is transformed into a different world from the first Kingdom Hearts game using "world cards" created from Sora's memories.

Unlike the previous game, the worlds are created from Sora's memories so many of the events experienced in Kingdom Hearts are relived in this game. Sora encounters memory-based versions of Disney characters that he has met before, except for Deep Jungle in Tarzan. The individual plotlines differ from the first game and revolve around the theme of memory. Chain of Memories introduces Twilight Town as a world created from memories on "the other side of [Sora's] heart", in addition to the original worlds of Kingdom Hearts.

Sora returns as the game's protagonist with many of the other characters from the first Kingdom Hearts also reappearing. Chain of Memories features numerous characters from both the Final Fantasy series and the Disney animated features canon. As each world and the related characters are recreated from Sora's memories, the characters interact with Sora as if they had never met. The game also introduces several new characters, some of which are members of the enigmatic Organization. Other new characters include Naminé, a young girl capable of manipulating memories, and DiZ, a mysterious man concealed by red robes and bandages. Riku appears as a playable character in the second story mode. After being sealed in the realm of darkness, he heads to the basement of Castle Oblivion, aided by King Mickey Mouse and DiZ.

Six members of the Organization serve as antagonists; four appear in Sora's story mode, and the other two in Riku's. Sora encounters Marluxia, the lord of Castle Oblivion; Larxene, Marluxia's assistant; Axel, a double agent with hidden loyalty; and Vexen, Marluxia's unwilling collaborator while Riku battles Zexion and Lexaeus, Vexen's allies. Ansem also appears in Riku's story as an entity that attempts to control him. Many of the Disney villains return via memory-based recreations.

As Sora, Donald, Goofy, and Jiminy Cricket are searching for Riku and King Mickey, a man dressed in a black, hooded coat appears and directs Sora towards a massive fortress called Castle Oblivion. Upon entering, the friends realize they have forgotten their abilities. The hooded man explains that as they go deeper into the castle, they will lose more memories, but will uncover new memories in the process. He creates a deck of cards made from their memories, and tells them that everything they encounter in this castle will be based on their memories.

Sora ascends the castle, and faces off against other hooded figures who are part of a group called the "Organization". As Sora loses his memories, he gradually appears to remember a girl named Naminé as an old friend of his. He learns from Organization member Larxene that Naminé is being held prisoner in the castle. He also clashes with a replica of Riku. This replica was created and controlled by another Organization member, Vexen, which both Sora and the replica himself believe to be the real Riku. Axel, an Organization double agent, kills Vexen for his "betrayal" to the Organization, but later releases Naminé and allows her to meet Sora in person. Sora discovers that Naminé has been manipulating his memories under the orders of Marluxia—the lord of Castle Oblivion and the man who lured Sora to Castle Oblivion—as part of his and Larxene's plan to overthrow the Organization. Sora climbs to the highest floor and defeats Larxene and Marluxia, after which Naminé puts Sora and his friends into pod-like machines to help them regain the memories they have lost. However, this process will cause them to forget the events that transpired in the castle. Before they are put to sleep, Sora and Naminé promise to meet again as real friends after he reawakens.

In Reverse/Rebirth, which occurs concurrently with the game's main story, Riku is transported from the realm of darkness to Castle Oblivion's deepest basement. As he traverses the castle, he fights figments of previous enemies to combat his inner darkness. Vexen fights Riku to obtain his data and creates Riku’s replica to counter Marluxia's plan. Ansem, still possessing Riku's body, tries to regain control of Riku. However, Mickey's power keeps Ansem at bay. Along the way, Riku battles and defeats Lexaeus, a member of Vexen's circle, only to be dragged into the realm of darkness. However, he is saved by Mickey before Ansem nearly succeeds in taking Riku's body as his own. With Marluxia eliminated, another of Vexen's allies, Zexion, attempts to dispose of Riku by drowning him in light. Riku is saved by Naminé disguised as Kairi, who helps him to control his darkness, allowing him to defeat Zexion. Riku later meets DiZ, an enigmatic individual interested in him who sends him to find Naminé. Riku's replica, who has learned of his altered memories, seeks to justify his existence by killing Riku, only to be destroyed by him. Riku chooses to face Ansem upon learning from Naminé that Ansem lives in his heart, and defeats him after DiZ summons him for Riku to fight. Riku then sets out on a journey to utilize both his darkness and light, with Mickey as his companion.

The idea for an intermediary title was developed after director Tetsuya Nomura and his team had already begun to develop ideas for the second Kingdom Hearts game, which he had intended to be set a year after the original. Originally titled Kingdom Hearts: Lost Memories, Nomura changed the name to match the overall outline of the story, while still reflecting the theme of memories. Chain of Memories was developed to bridge the gap between Kingdom Hearts and Kingdom Hearts II. Like most sequels, Kingdom Hearts II was planned to have the character start from the beginning, ability-wise. To explain the loss of abilities gained in the previous game, Nomura had the story revolve around Sora's memories getting corrupted and implemented the card battle system to symbolize Sora's various memories.

Nomura was hesitant about releasing a Kingdom Hearts title on the Game Boy Advance, feeling that the 3D graphics of the original game would not translate well into 2D. Nomura changed his position after hearing that children wanted to play Kingdom Hearts on the GBA. After exploring ideas for the gameplay, he felt that a 2D Kingdom Hearts game would be possible, and that it could still feel like and play like what gamers were used to in the original. Meanwhile, Nomura wanted to give the game a "lighter tone" than the PlayStation 2 games.

Chain of Memories was announced along with Kingdom Hearts II at the Tokyo Game Show in September 2003. Initial details included the switch to 2D graphics, the use of cards to perform attacks, and that compressed movies would be utilized in some cut scenes. The cut scene animations were rendered using the graphical engine of the PlayStation 2 iteration and then encoded for the Game Boy Advance by using a technology developed by Japanese company, AM3. To help market the game, Disney and Square Enix launched official Japanese websites. A playable demo was first made available to the public at the 2003 Jump Festa in Japan; this demo and subsequent demos highlighted the card-based combat system. Aside from information gathered from the opening sequences, most details regarding the story were kept secret until the release.

The card-based gameplay of Chain of Memories would later serve to inspire the gameplay of Jupiter's next game, The World Ends with You; originally, the team envisioned a similar card game-based system taking place on the lower screen of the Nintendo DS, but eventually this morphed to a battle system taking place on both screens, with a card game controlled on the upper screen.

Music from the original Kingdom Hearts was reused in Chain of Memories including the main vocal theme "Hikari" (光) in the Japanese release. An English version titled "Simple And Clean", is used in the Western releases. Additional and reworked tracks were created for the PlayStation 2 rerelease, Kingdom Hearts Re:Chain of Memories. Since the music is reused from the original, a standalone Chain of Memories soundtrack was never released. The new reworked tracks, however, are included on two CDs in the Kingdom Hearts Original Soundtrack Complete.

Due to the technological limitations of the Game Boy Advance cartridge size, voice acting was kept to a minimum, primarily during the battle sequences. Many characters from Kingdom Hearts continued to be voiced by the same cast, the Japanese version used the following voice actors for new characters: Keiji Fujiwara as Axel; Tatsuya Kando as Vexen, Marluxia, and Lexaeus; and Rieko Katayama as Larxene. Voice clips from the first Kingdom Hearts were inserted into Chain of Memories. The English version has no dialogue; the voices during Organization battles are replaced with simple grunts, laughter, and other battle cries.

Like its predecessor, a great deal of merchandise was produced to help market the release of the game. Square Enix released two products to coincide with the release of the video game. The first was a limited edition Kingdom Hearts Game Boy Advance SP set released only in Japan. The set contained the game, a "Kingdom deep silver" GBA SP with the Kingdom Hearts logo, and a carrying strap. The second was a Kingdom Hearts trading card game produced by Tomy. The TCG featured starter decks, playing mats, and booster packs. Fantasy Flight Games later acquired the rights to market it to English-speaking countries. In 2007, a remake for the PlayStation 2, titled Kingdom Hearts Re:Chain of Memories was released along with Kingdom Hearts II Final Mix in a set, Kingdom Hearts II Final Mix+. A manga series ran in Monthly Shōnen Gangan in Japan, and was later released in the United States. It is accompanied by three novels—two set during Sora's storyline and the third during Riku's story. Like with the Final Fantasy games and the first Kingdom Hearts game, Square released an Ultimania book on Kingdom Hearts: Chain of Memories following the release of the game. In North America, BradyGames released a strategy guide with a comprehensive walkthrough.

Kingdom Hearts: Chain of Memories was remade for the PlayStation 2, titled Kingdom Hearts Re:Chain of Memories. It was developed by Square Enix's fifth Product Development Division, based in Osaka, and released as the second disc of Kingdom Hearts II Final Mix+ in Japan on March 29, 2007 and as a standalone title in North America on December 2, 2008. It has not been released in Europe or Australia for the PlayStation 2, but has seen a worldwide release as part of Kingdom Hearts HD 1.5 Remix. The remake includes polygonal 3D battles and worlds using the same graphics as Kingdom Hearts, as well as voice acting and an improved soundtrack. While the card-based battle system and room synthesis aspects of the gameplay stayed mostly the same, there were additions, such as the "Reaction Command" function from Kingdom Hearts II. Voice-acted scenes occur only in Castle Oblivion, as well as in the Destiny Islands and Twilight Town simulations. The remake also includes new cutscenes and battles that were not in the original game. IGN ranked it as the 92nd best PlayStation 2 game. The staff felt that it stood out among other card-based RPGs.

Like the first Kingdom Hearts, Chain of Memories was adapted into a manga by Shiro Amano, following the same plot as the video game. It was serialized in Square's Monthly Shōnen Gangan in Japan, then released in two volumes in Japan and later in the United States by Tokyopop. The first volume was released in Japan on October 22, 2005. A year later, it was released in English on October 10, 2006, followed by the second volume on February 6, 2007.

The manga series has had moderate success. The first volume was ranked 112th on USA Today's "Top 150 best sellers" during the week of its release. IGN praised Amano's renditions of the characters and the humor added into scenes. They also commented the weak elements of the game lessened the manga's overall quality. The series was followed by a third manga series, Kingdom Hearts II. The Chain of Memories manga series was re-released in a boxed set in the United States on October 9, 2007.

In September 2012, Square Enix announced Kingdom Hearts HD 1.5 Remix a compilation for the PlayStation 3 to include both Kingdom Hearts Final Mix and Re:Chain of Memories in high definition and trophy support. Additionally, the collection includes HD cinematic scenes from Kingdom Hearts 358/2 Days. It was released in Japan on March 14, 2013 and in North America on September 10, 2013. Releases on September 12, 2013 for Australia and September 13, 2013 for Europe marked the first time Re:Chain of Memories was available in both of those territories. This version was later ported to the PlayStation 4 as part of Kingdom Hearts HD 1.5 + 2.5 Remix, released in March 2017.

While the least successful in the series commercially, Chain of Memories received generally positive reviews and met with successful sales figures. In Japan, it sold 104,000 units in 48 hours, a record for a Game Boy Advance title at the time. Its positive debut sales placed it in the top spot of sales charts in Japan. In the first month of its North American release, it was ranked 1st on GameSpot's ChartSpot for portable systems and 6th for all consoles. By February 2005, it had sold over one million copies in Japan and North America. Worldwide sales of the game reached 1.50 million copies by the end of 2006. In the United States alone, it sold 900,000 copies and earned $28 million by August 2006. During the period between January 2000 and August 2006, it was the 24th highest-selling game launched for the Game Boy Advance, Nintendo DS or PlayStation Portable in that country. By late 2009, Chain of Memories had sold over 1.55 million copies worldwide, with 200,000 in PAL regions, 410,000 in Japan, and 940,000 in North America.

The game received mostly positive reviews from critics. The card-based battle system received mixed reviews. GameSpot called it "unwieldy", while GameSpy called it "engaging" and Game Watch called it original. Reviews also cited that the card battle system was awkward and made it difficult to plan strategies. G4 commented that the gameplay was well suited for portable play and that it successfully combined card battles and random dungeons, "two much-maligned RPG" elements. Some critics found the Room Synthesis to be far too linear. The most frequent praise went towards the story. IGN called it an "engrossing storyline that actually changes up after the adventure comes to an end" and rated the presentation a 10 out of 10.

The quality of the graphics was well received, particularly the cut scenes. IGN cited them as "wonderfully produced FMV sequences". GameSpot stated that the movies were true to the art style of the original and were on par with GBA video paks. They also commented on the detailed and well animated game sprites. Game Watch described the event scenes as "high quality". Many critics stated that though the graphics were not as good as the PlayStation 2 predecessor, they were very good for a GBA game. G4 complimented the graphics stating that Chain of Memories was "one of the best-looking GBA games out there."

During the 8th Annual Interactive Achievement Awards, the GBA version received a nomination for "Handheld Game of the Year".

• List of Disney video games

• Kingdom Hearts: Chain of Memories Japan official website
• Kingdom Hearts: Chain of Memories at IMDb