Aqua's History
Aqua, alongside Terra, is one of Eraqus's pupils. Like Terra, Aqua also has a dream of becoming a Keyblade master.
One day, a suspicious man named Master Xehanort arrived and gave Eraqus a new pupil, Ventus. Terra and Aqua start to question him but this ends up troubling him and he passes out. Eraqus explains that this is because Ventus has lost his memories so Aqua takes on to caring for him. While countless days pass, one day Ventus wakes up in front of Aqua. The next day, Aqua takes the Mark of Mastery exam with Terra and becomes a Keyblade Master with Terra failing due to not being able to keep control of his Darkness. After Terra and Ventus leave the Land of Departure, Aqua leaves last due to a conversation with Master Eraqus telling her to bring Ventus back, he also asks her to keep a close eye on Terra and to also bring him back immediately due to his Darkness.
Aqua, Ven, and Terra come across many Disney characters along the way and fight of hordes of Unversed. Aqua later ends up at Radiant Garden with Mickey Mouse and meets Kairi, who touched Aqua's Keyblade in fright, unintentionally performing a Keyblade Inheritance Ceremony. They protect her from the Unversed and in return, Kairi gives Aqua flowers which turn into the Destiny's Embrace Keyblade. She then places a protective charm on Kairi to aid her in the future. Aqua believes the meeting was not a coincidence. Aqua later meets up with Terra and Ventus, but the reunion is short-lived as they team up to battle a massive Unversed. They defeat it, but things take a turn for the worse, while Aqua tries to tell Ventus that he should go home now, Terra and Aqua begin to argue about Master Eraqus's orders and ends up revealing to Terra that she was sent to watch him. Hurt by this, Terra leaves and Ventus calls Aqua awful claiming that she has taken the status of Keyblade Master too seriously and leaves behind Terra, while Aqua stays to contemplate.
After meeting Merlin, Aqua goes to the town square and meets Vanitas, who taunts her by asking about Ventus and if has gotten stronger. When Aqua asks what he means, Vanitas attacks, and the pair fight a vicious battle. Aqua emerges victorious, but Vanitas simply leaves, making a comment about her being his backup plan. Aqua then resolves to defeat Vanitas to protect Ventus and Terra. Ventus then appears, asking to go with Aqua. But Aqua tells him to go home and departs.
While in Neverland, Aqua encounters Peter Pan and the Lost Boys, joining them on their treasure hunt. They later find their treasure chest, filled with wooden swords and Ventus's wooden Keyblade. Peter Pan tells Aqua that Ventus left the toy there as he no longer needed it. Aqua then senses someone nearby and goes off to investigate. She then encounters Vanitas again, this time with Ventus's cherished Wooden Keyblade. The dark enigma cruelly mocks Aqua's actions and snaps the toy weapon in two. Greatly enraged by this, Aqua battles and defeats him again, but is exhausted by the fight and passes out. While unconscious, she reminisces about the last starry night she spent with Terra and Ventus at the Land of Departure. She soon recovers and departs soon after.
At one point Aqua and Terra come to Destiny Islands and meet two young boys by the name of Sora and Riku. Aqua sees the strong bond between the two friends and advises Sora to help Riku if he ever falls into darkness; though she initially intends to grant Sora the power to use the Keyblade, she decides against it upon discovering that Terra had already done it for Riku, not wishing to put the two innocent children through the ordeals she and Terra have faced. Aqua later encounters an unconscious Mickey drifting in space and takes him to the Mysterious Tower, where she hears of Eraqus's death from Yen Sid and heads to the Keyblade Graveyard to meet up with Terra and Ven. They are confronted by Master Xehanort and his apprentice, Vanitas and a great battle takes place. After she catches a frozen Ventus, they are confronted by Braig and Aqua fights him. After fighting Braig she is knocked out by Vanitas and is later woken up Mickey and finds Ventus above on the cliff but then it is revealed that Ventus is under Vanitas's influence and he now wields the χ-blade.
He then explains his plan to unlock Kingdom Hearts and reenact the Keyblade War. Aqua screams at him to shut up and give Ventus his heart back. Once she destroys the χ-blade, Aqua loses consciousness and she ends up at Yen Sid's Tower with Ventus, who has lost his heart. She takes Ven back to the Land of Departure and places his unconscious body in a throne. She takes Eraqus's Keyblade and transforms the world into Castle Oblivion to keep Ventus safe. She then tracks down a possessed Terra in Radiant Garden.
Failing to bring Terra back to his senses, Aqua fights and defeats Xehanort; subsequently, Xehanort stabs himself in the chest with his own Keyblade in an attempt to lock Terra out as a horrified Aqua looks on. As Terra-Xehanort falls through a portal into the Realm of Darkness, Aqua dives in after him, but quickly realizes that she will be unable to save them both.
Instead, Aqua sacrifices her armor and Keyblade to save the dark being that had once been her dear friend, sending him back into the Realm of Light while she remains behind; unbeknownst to her, her actions, despite being valiant and heroic, will unintentionally doom the worlds to twelve years of suffering and destruction by the Heartless at the hands of Ansem, Seeker of Darkness and Xemnas - the heartless and nobody of what was once her friend - and the evil fairy, Maleficent.
Now stuck in the Realm of Darkness, Aqua is attacked by several giant Heartless and decides to just allow them to destroy her, but is saved by Terra and Ventus's Keyblades. She is then reminded of the people she's connected to. With renewed trust in her friends, Aqua continues on.
As she travels she sees a large circle of light form above her, only for a powerful column of darkness to shoot out of it in front of her. Seemingly unshaken by this she presses forwards and encounters several Pureblood Heartless, namely Shadows, Neoshadows, and Darkballs.
After traveling deeper into the Realm of Darkness Aqua senses something stalking her, and comes face to face with a large Heartless that attacks her. To prevent it from attacking her she uses a Fire spell, only for it to leap over her. Getting a closer look at it, Aqua determines it is not an Unversed and takes a battle stance to fight it.
After defeating the Heartless, Aqua continues walking, eventually coming out in a clearing and looking up. Surprised she recognizes the Castle of Dreams surrounded by clouds of darkness.
