An expanded re-release of the game featuring new and additional content, Kingdom Hearts II Final Mix, was released exclusively in Japan in March 2007.

[2] Sora, the protagonist of the first two games, returns to search for his lost friends while battling the sinister Organization XIII, a group of antagonists previously introduced in Chain of Memories.

Like many traditional role-playing video games, Kingdom Hearts II features an experience point system which determines character development.

[13] Combat in Kingdom Hearts II takes place in real-time and involves hack and slash elements with button presses which initiate attacks by the on-screen character.

[13] A new feature is the "Reaction Command", special enemy-specific attacks that are triggered when the player presses the triangle button at the correct time during battle.

Although retaining its basic purpose of travel, the system was completely redone to resemble a combination of rail shooter and "Disney theme park ride".

[18] Other original characters include Riku, who is briefly playable at the game's climax, and Kairi, who are Sora's friends from his home world of Destiny Islands; Roxas, a boy who can also wield the Keyblade and is playable in the game's beginning sequence; Naminé, a girl with the power to manipulate memories; and DiZ, a man who wears red robes and has a vendetta against Organization XIII, and is later revealed to be Ansem the Wise, the mentor of Xehanort.

These party members include Fa Mulan, a woman who passes as a man to take her ailing father's place in the army; Jack Sparrow, a pirate who seeks to reclaim his ship, the Black Pearl; Simba, a self-exiled lion and the rightful king of the Pride Lands; and Tron, a security program in Hollow Bastion's computer network who seeks to end the dictatorship of the Master Control Program.

[21] Sora, Donald, and Goofy awaken in the real Twilight Town and meet King Mickey and Yen Sid, who send them on another journey to find Riku and uncover the Organization's plans.

During a visit to Hollow Bastion, they reunite with Mickey, who explains that the Heartless "Ansem" they defeated is an imposter named Xehanort, whose Nobody, Xemnas, is the Organization's leader.

Many of the original voice actors from the first Kingdom Hearts reprised their roles; Miyu Irino and Haley Joel Osment as Sora, Mamoru Miyano and David Gallagher as Riku, and Risa Uchida and Hayden Panettiere as Kairi.

New voice actors included Kōki Uchiyama and Jesse McCartney as Roxas, Iku Nakahara and Brittany Snow as Naminé, and Genzō Wakayama and Christopher Lee as DiZ.

Many actors reprised their Disney roles for the game, including Ming-Na Wen as Mulan, James Woods as Hades, Bruce Boxleitner as Tron, Chris Sarandon as Jack Skellington, Angela Lansbury as Mrs. Potts, Kenneth Mars as King Triton, and Zach Braff as Chicken Little.

[11] An attack animation was also altered; in the Japanese version, Xigbar combines his two hand-held guns to create a sniper rifle, which is used to shoot the player's party during the telescoping sight sequence.

The death of Organization XIII member Axel was slightly edited; in the original, he bursts into flames during his suicide attack, while in the English version he simply fades away after using up all of his power.

[65] Patrick Gann of RPGFan deemed the partner artificial intelligence to be superior to the first game,[68] whereas Haynes denounced it as "absolutely terrible", attributing this to the omitted ability to issue AI commands.

[66] The quick time events were a generally welcomed addition, with Luke Albiges of Eurogamer regarding their quality and impact to be on par with the knife fight scene in Resident Evil 4.

[62] Reviewers complimented the camera's increased responsiveness, which Haynes attributed to the altered control method from the shoulder buttons to the right thumbstick.

[58][68] The RPG elements were described as light, with Haynes calling them a "casualty" of the increased emphasis on combat; he remarked that items were "practically useless" due to a lack of need to use them in certain places as in the first game.

[3][61][66] Although Albiges considered the quality of the locales to be consistently high (singling out Port Royal for praise),[9] others lamented the decreased size and increased linearity of the worlds, with Haynes particularly describing Halloween Town and Atlantica as "shadows of their former selves".

[63][68] Haynes admired the main characters' changing appearance depending on the world they are visiting,[66] and Villoria noted that the enemies were also visually adapted to their environments, which he said granted them personality.

[3] Mielke complimented Nomura's "eye for epic drama" previously observed in Final Fantasy VII: Advent Children, which he said "touches you where games like, say, God of War never will".

[57] Gouskos said that the interactions with the frequently changing cast of characters made up for the game's lack of challenge, and that the use of lines from the original Disney films enhanced the sense of immersion.

However, she deplored the "aloof" dialogue for the Square characters, singling out an instance in which Final Fantasy VIII antagonist Seifer declares "We totally owned you lamers!".

[67] Fischer, likening the general plot to "a long episode of Quantum Leap with permanent guest stars Donald and Goofy", described the storyline as linear and somewhat nonsensical, but "endearing and twisty" enough to hold players' attention.

[61] Bettenhausen and GamePro's Bones respectively dismissed the prologue as "woefully boring" and "sluggishly slow",[58][60] though Reiner stated that "In a devilish yet remarkable plot twist, you may not want Sora back".

Released along with Final Mix, Kingdom Hearts -Another Report- was a hardback book which includes game information, visuals by Shiro Amano, and a director interview.

[83] In a Weekly Shōnen Jump interview with Nomura, he expressed interest in a possible international version of Kingdom Hearts II, although there were no definite plans.

[90] A manga series based on the game started its serialization in the June 2006 issue of the magazine Monthly Shōnen Gangan, published by Square Enix.

The novel depicts extra scenes that were added in the Final Mix version, such as interaction between Organization XIII members and between Axel, Naminé and Riku.