Every epic saga needs a place where it all begins. With Kingdom Hearts, it begins with Kingdom Hearts: Birth By Sleep.
Note: Although the series does actually start with Kingdom Hearts Unchained, the main focus of the series narrative does not begin until this game.
In a mysterious sanctuary known as The Land of Departure, three young friends named Terra, Ventus and Aqua are training to become wielders of weapons known as Keyblades. Under the tetulage of Master Eraqus, they are hoping to achieve the rank of Keyblade Masters. On the day before Terra and Ventus take their exam, the three friends forge an unbreakable bond using mysterious keychains known as Wayfinders.
During the exam, which is overseen by Master Eraqus and another Keyblade Master named Xehanort, Aqua manages to ascend to the role herself. Terra on the other hand does not pass the exam, due to the presence of darkness within his heart, instead of a heart filled with light.
During the aftermath, Terra is encouraged by Xehanort to channel the darkness within his heart, whilst secretly colluding with a mysterious teenage figure comprised of dark energy. Sometime later, Eraqus informs Terra and Aqua that Xehanort has gone missing, and assigns them to locate the missing Master. The group also discovers that Unversed, mysterious creatures made of darkness have begun to appear in otherwise peaceful worlds.
Terra decides to leave The Land of Departure, closely pursued by Ventus who is concerned for the wellbeing of his friend. Aqua and Eraqus are gravely concerned, and Aqua sets out to bring Ventus back home whilst searching for Xehanort. After travelling through various worlds, the three friends bond is put to the test, with several Disney villains such as Maleficent and the Evil Queen manipulating Terra’s brewing darkness for their own twisted ends.
During his journey, Terra is summoned by Xehanort to a mysterious barren place, and tells him that it is his fault that the worlds are in danger. He informs Terra that Ventus used to be his pupil, but during his training, Ventus fell to darkness. Xehanort was forced to extract the darkness from Ventus’s heart, accidentally causing the Unversed and a mysterious boy like figure named Vanitas to be born. Convinced of Xehanort’s apparent innocence, Terra pledges to destroy Vanitas, hoping that his own darkness will be vanquished as a result.
Aqua begins to believe Eraqus’s deductions that Terra’s darkness is something to fear, despite her loyalty to her life long friend. The three friends eventually reunite in a world known as Radiant Garden. Aqua saves the live of a young girl named Kairi, with the help of a young Keyblade wielder named King Mickey. In order to protect Kairi in the future, Aqua casts a spell that will ensure that her pure heart filled with light will be protected if anyone tries to harm her.
Aqua and Ventus encounter Vanitas, who taunts their apparent lack of strength. Terra manages to find Xehanort, along with Braig, one of his assassins. After managing to break away from their influence, Terra continues to travel through the worlds to bring Ventus back home. After taking down a large Unversed as a team, Terra, Ventus and Aqua are pulled apart by the conflict that has been brewing during their time apart.
For reasons unknown, Terra and Aqua are summoned to the Destiny Islands, a mysterious tropical paradise they have never visited. Terra arrives first, and meets two young boys named Riku and Sora. Sensing the potential to wield a Keyblade in his future, Terra allows Riku to touch his Keyblade, which will allow Riku to summon one of his own when the time arrives.
When Aqua arrives on the Destiny Islands, she also meets the two boys, and senses that Terra has given Riku the potential of wielding a Keyblade. Sensing the same potential within Sora, Aqua allows him to touch her Keyblade, asking him to protect Riku if he should ever be in danger.
Eventually, Terra and Ventus return home to the Land of Departure. Terra is tricked into thinking that Eraqus plans to kill Ventus, as Vanitas is a being forged from his extracted darkness, and the reason for the existence of the Unversed. Filled with rage, Terra uses his darkness during the fight and accidentally slays Master Eraqus. Ventus is taken away after the incident, and ends up in a wasteland known as the Keyblade Graveyard.
After leaving the Destiny Islands, Aqua learns of Eraqus’s demise after speaking with Master Yen Sid, who lives in a secluded world known as the Mysterious Tower. Aqua doesn’t believe that Terra would do something so awful, so leaves the Mysterious Tower to learn the truth for herself.
Terra and Aqua eventually arrive at the Keyblade Graveyard and locate Ventus, only to be confronted by Vanitas and Xehanort. Their plan is to reunite Vanitas with Ventus, which will create a enhanced form of the Keyblade known as the ϗblade. Xehanort then reveals that Ventus’s split was not an accident like he had claimed, and that by using the ϗblade, Xehanort can access a place known as Kingdom Hearts, where all hearts in the universe are born.
During the ensuing battles, Xehanort reveals to Terra that he plans to use Terra’s darkness to steal his body, thus obtaining a form of eternal youth. He succeeds, creating a being known as Terranort. The fusion of Ventus and Vanitas takes place, but Ventus manages to regain control of his heart and break the ϗblade, which destroys Vanitas, seals away Kingdom Hearts and throws Aqua and Ventus into the World of Darkness, a place where everyone who falls to darkness ends up.
They are rescued by King Mickey, who brings them back to the Mysterious Tower, where he has been training under Master Yen Sid. Because of the battle inside his heart, Ventus’s soul has splintered into pieces once again. Only this time, he will not awaken from his sleep until it has been healed.
Aqua takes Ventus’s body back to the Land of Departure, and uses her keyblade to lock the sanctuary away with her sleeping friend inside. She then goes to locate Terranort in Radiant Garden, and after a confrontation in the World of Darkness, Aqua throws Terra back to the World of Light, unaware of the fact that Xehanort is still inside of her friend’s body.
Terranort has seemingly lost his memory, and is welcomed to work in Radiant Garden alongside a respected man named Ansem the Wise. Meanwhile, Ventus’s soul finds a place to sleep inside of a young boy with a welcoming heart, whose name just happens to be Sora.
Ten years pass in the World of Light, with an unknown amount of time passing in the World of Darkness. Terra’s soul is still inside his body and clashing with Xehanort, spared by the soul of Master Eraqus who has given him the strength to survive. Aqua is still in the World of Darkness, fighting to find her way back home and rescue her friends.
Sora, who is now fourteen years old, begins to have strange dreams, paving the way for the original game to begin.
Next Chapter – Chapter 1: Kingdom Hearts 1