Originally released only in Japan on December 26, 2002, Kingdom Hearts Final Mix has several events and a number of gameplay tweaks that are not in previous releases. Spoken dialogue is in English, with Japanese subtitles. 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. A gameplay option allows the player to skip cutscenes after seeing them once. 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.
Several new cutscenes were added. The first, shown after Sora fights Leon in Traverse Town, has Riku lost in Hollow Bastion, calling out for his friends and Maleficent looking on. Another, played after Sora speaks to Kairi in the underground waterway in Traverse Town, showed Riku lost in the Realm of Darkness after Ansem, Seeker of Darkness took his body. There, he is assisted by King Mickey who reveals that he has the realm's Keyblade. Neither of these cutscenes used any new audio and instead the subtitles were seen on a black screen. An optional cutscene was a confrontation between Cloud and Sephiroth, seen after the player defeats Sephiroth. Cutscenes were provided for the Unknown, using spliced voice acting for Sora and Goofy, but shaking text on a black screen for the Unknown. A minor cutscene was also added near the start of the game on the second day on Destiny Islands, where it is revealed that the lucky charm Kairi makes out of Thalassa Shells is the Oathkeeper charm she later gives to Sora.