Editing Kingdom Hearts Birth by Sleep

An enhanced version, ''[[Kingdom Hearts Birth by Sleep Final Mix]]'', features more enemies, additional scenes, and many other elements like expanded worlds, and was released in Japan on January 20, 2011.

[[File:Flashback The Wooden Keyblade 01 KHBBS.png|thumb|left|Terra, Aqua, and Ventus take a break from their training.]]

''Kingdom Hearts Birth by Sleep'' begins in the [[Land of Departure]], where three Keyblade wielders and close friends—[[Terra]], [[Aqua]], and [[Ventus]]—train to become Keyblade Masters under [[Eraqus]]. To achieve this rank, Keyblade Apprentices must take the [[Mark of Mastery exam]] once they come of age. Terra and Aqua take this test together, but while Aqua passes the test, Terra is deemed unfit to become a Keyblade Master due to the abundant darkness in his heart. Afterward, a group of mysterious creatures called the [[Unversed]] begin to surface in other worlds, and another Keyblade Master, [[Master Xehanort|Xehanort]], disappears without a trace. Terra is sent to destroy the Unversed and find Master Xehanort, who had earlier encouraged him to embrace the darkness in his heart if he desires the strength to become a Keyblade Master. Ventus, meanwhile, is goaded into following Terra by Xehanort's mysterious apprentice [[Vanitas]], against Eraqus's wishes. Aqua is dispatched by Eraqus to survey Terra and keep him from falling into darkness, as well as to bring Ventus back to the Land of Departure.

Upon arriving in other worlds, Terra, Aqua, and Ventus encounter various Disney characters, new and old, fighting off hordes of Unversed along the way. Among the characters they meet is [[Mickey Mouse]], apprentice of the sorcerer [[Yen Sid]], who is also on a mission to destroy the Unversed. Terra ends up attracting the attention of several Disney villains, who offer him the whereabouts of Master Xehanort in exchange of assistance for their own dark agendas. Terra reasons that Master Xehanort is after the seven [[Princesses of Heart]]—maidens who lack darkness in their hearts—and encourages Aqua to help them strengthen the light in their hearts, hoping it will draw Master Xehanort out. However, Aqua and Ventus grow increasingly concerned for Terra when they hear rumors of him committing sinister deeds throughout other worlds. The three briefly reunite at [[Radiant Garden]], where Aqua meets [[Kairi]], a young girl containing a strong and pure light in her heart, and helps strengthen her light. Aqua and Ventus also confront Terra, who distances himself from them to keep them out of the way of his increasingly dangerous dark powers. Terra and Aqua try to convince Ventus to return to the Land of Departure, but he refuses until he is certain Terra won't fall into darkness.

Terra and Aqua eventually find themselves at [[Destiny Islands]], where they encounter two young boys, [[Sora]] and [[Riku]]. Terra sees potential within Riku and deems him worthy of one day wielding the Keyblade, while Aqua senses strong ties with Sora and Riku to Ventus and Terra, respectively. Ventus, meanwhile, comes across Master Xehanort, who reveals his intentions to use Ventus's heart to create a final Keyblade known as the [[χ-blade]], something Master Xehanort says Master Eraqus had known all along. Ventus returns to the Land of Departure to confront Eraqus, who tries to erase Ventus to prevent Master Xehanort's plans from succeeding. However, Terra, who had been sent there by Xehanort, misinterprets the situation and attacks Eraqus, teleporting Ventus to safety. As soon as Terra realizes his error, Master Xehanort arrives and cruelly kills Eraqus and tells Terra to go to the [[Keyblade Graveyard]], leaving the Land of Departure to be consumed by darkness. At Destiny Islands, Ventus once again encounters Vanitas and learns of his hazy past: Ventus was once Master Xehanort's apprentice, but his heart was deemed too frail for Master Xehanort to use him as he intended, so he extracted the darkness in Ventus's heart and used it to create Vanitas. As with Terra before him, Ventus is instructed by Vanitas to go to the Keyblade Graveyard. Aqua, in the meantime, learns of Eraqus's death from Yen Sid, who tells her to go to the Keyblade Graveyard as well.

[[File:The Last Bastion of Free Will 03 KHBBS.png|thumb|Terra becomes a vessel for Xehanort.]]

Terra, Aqua, and Ventus gather at the Keyblade Graveyard, where the remains of the mysterious [[Keyblade War]] are found. Master Xehanort appears with Vanitas and reveals his plan to use the χ-blade to unlock [[Kingdom Hearts]] and unleash the forbidden secrets of the Keyblade War onto the various worlds, as well as to use Terra's body as a new vessel for his own heart so that he may survive long enough to see his plans come to fruition. An epic battle ensues, with Xehanort freezing Ventus, and Vanitas knocking Aqua unconscious. In his rage, Terra unleashes the darkness in his heart, inadvertently allowing Xehanort to unlock his own heart and successfully transfer it into Terra's body, which results in the birth of a new, younger [[Terra-Xehanort|Xehanort]]. However, Terra's mind continues to linger in his [[Lingering Will|discarded suit of Armor]], which comes to life and defeats Xehanort. Ventus, meanwhile, manages to thaw himself before Vanitas can kill Aqua, and discovers his dark counterpart to be the source of all Unversed. Vanitas merges with Ventus, possessing him and creating the χ-blade. Aqua awakens under Mickey's care, and the two fight the possessed Ventus while he battles Vanitas from within. Aqua shatters the χ-blade as Ventus destroys Vanitas, bringing an end to the Unversed, though Ventus's heart is lost in the process. The destroyed χ-blade unleashes a burst of light, which consumes everyone present and scatters them to the corridors of space, save for Terra's Lingering Will, which remains in the Keyblade Graveyard.

Mickey saves Aqua and Ventus and brings them to the [[Mysterious Tower]], where Aqua learns that Ventus has fallen into a deep sleep and will not awaken until his heart returns. Aqua brings Ventus back to the ruins of the Land of Departure, where she discovers Eraqus's Keyblade, and uses it to lock the [[Chamber of Waking]] and reshape the world into [[Castle Oblivion]]. After leaving Ventus within the Chamber, Aqua goes to Radiant Garden to battle Xehanort, who still inhabits Terra's body, but having lost some of his memories. After the fight, Xehanort attempts to unlock his heart, losing his memories completely in the process. Soon after, Terra's body starts sinking into darkness, but Aqua dives into the darkness and saves Terra from disappearing. Realizing her glider won't be able to make it back through the portal in time, Aqua sacrifices herself by discarding her armor and using it to guide her glider, Terra-Xehanort in tow, back through the portal leaving herself behind and falls into the Realm of Darkness.

Xehanort is discovered by [[Ansem the Wise]], ruler of [[Radiant Garden]], and goes on to become his apprentice. Ventus's wandering heart finds its way to young Sora, being absorbed into the boy's own heart. Meanwhile, Aqua walks along and is attacked by several Darksides. Initially, she draws Master Eraqus's keyblade, but upon seeing the number of Heartless, she decides to just allow them to destroy her. However, Aqua is saved by Terra and Ventus's Keyblades. Looking at her Wayfinder, she is then reminded of the people she's connected to. With renewed trust in her friends, Aqua continues on.

The game is divided into three separate scenarios, with each scenario surrounding an individual of the three main characters: Terra, Ventus and Aqua. Players are able to choose which of the three scenarios to play at the start of a new game. The order does not matter, although Terra > Ventus > Aqua is often recommended because Terra is the slowest, and playing him after Ventus/Aqua can feel agonizingly slow. Aqua is often recommended last because she has one extra scenario (or two if playing the ''Final Mix'' version), in which the finale of the game concludes. Magic is extremely important in Aqua's scenario, and the player will need to spend time learning how the Melding system works and get an idea of what sort of outcomes exist. Because of the final scenario(s), the player should prepare Aqua as much as possible before doing the final boss in her scenario.

Once all three of the scenarios are completed and all [[Xehanort Reports]] are collected, the [[Final Episode]] is unlocked. In the ''Final Mix'' version, the [[A Fragmentary Passage|Secret Episode]] is after the Final Episode.

===Multiplayer mode===

==Worlds and characters==