Kingdom Hearts II was re-released under the name Kingdom Hearts II Final Mix, which includes new content and was initially released exclusively in Japan. This version was localized and remastered in the Kingdom Hearts HD 2.5 Remix, which also includes Birth by Sleep and Re:coded, and released for PlayStation 3 and PlayStation 4.
The game takes place directly after the ending of Kingdom Hearts. Sora, after sealing the final door and rescuing Kairi, becomes a heartless. In order to protect himself, his body and memories were locked away during this time.
The prologue follows Roxas, a boy who lives in a Twilight Town. He, along with his friends Hayner, Pence, and Olette, are enjoying the final week of their summer vacation. Roxas has recurring dreams about Sora and his adventures, but is confused why he experiences them. As the days pass, more mysterious things start happening around Twilight Town and Roxas becomes detached from his friends. On the final day of his vacation, Roxas becomes invisible to nearly everyone in Twilight Town; the only recognition he recieves is from a disembodied voice, beckoning him to the old mansion. It turns out members of an elite group of Nobodies, called Organization XIII, are attempting to use Roxas' as a vessel for Sora's memories and are monitoring the progress from a computer laboratory in the basement. As such, the Twilight Town he was living in was a virtual version, recreated using various data from the real Twilight Town. Roxas finds out his true purpose, that he never supposed to exist. After exploring the mansion some more, he eventually stumbles upon Sora's holding chamber, opening it up. As the cell opens up, Roxas accepts his fate, lamenting about his summer vacation being over.