Aqua is a character from Square Enix's video game franchise Kingdom Hearts. First making cameo appearances in Kingdom Hearts II and its updated version Final Mix, she is introduced in the prequel Kingdom Hearts Birth by Sleep alongside her friends Terra and Ventus. The three are Keyblade apprentices training under Master Eraqus, and are the playable protagonists. As the only one among her friends to obtain the rank of Keyblade Master, Aqua is assigned to monitor Terra and Ventus as she combats dark creatures known as the Unversed.

Kingdom Hearts Birth by Sleep is an action role-playing video game developed and published by Square Enix in collaboration with Disney Interactive Studios for the PlayStation Portable, serving as the sixth installment in the Kingdom Hearts series. The game was released on UMD in Japan on January 9, 2010, in North America on September 7, 2010, and in PAL regions on September 10, 2010. An international version of the game titled Kingdom Hearts Birth by Sleep Final Mix was released in Japan in January 2011, featuring the changes made in the non-Japanese versions. A direct sequel, Kingdom Hearts 0.2: Birth by Sleep - A Fragmentary Passage, was released in January 2017 as a part of a bundle of games called Kingdom Hearts HD 2.8 Final Chapter Prologue.