The Western releases include a number of new features, including the Sticker Album, a new boss, new Keyblades, abilities, mini-game maps and songs, and the addition of Critical Mode. Like Kingdom Hearts and Kingdom Hearts Chain of Memories, the main theme song for the game is ' Simple and Clean', performed by Utada Hikaru. The story focuses primarily on Terra, Aqua and Ventus, three young Keybearers from before Sora's generation, although the game also gives focus to the origins of Sora and Xehanort, delving deep into the mysteries of Xehanort's bleak past and forgotten memories as well as how Sora and Riku came to wield the Keyblade in the first place. The game serves as a prequel to the first game, taking place ten years before. Kingdom Hearts Birth by Sleep was developed by the same team that created Kingdom Hearts Re:Chain of Memories. The game's name is shared with the secret video at the end of Kingdom Hearts II Final Mix, ' Birth by Sleep', which depicts a stylized version of a scene from the game. It was originally created for the Sony PlayStation Portable (PSP).
Kingdom Hearts Birth by Sleep is the sixth game in the Kingdom Hearts series. Everything will link back to the beginning.' -Tagline ' Destiny is never left to chance.' -Alternate Tagline
