ContextNot familiar with the Kingdom Hearts series? This page gives a very brief overview of the series, Birth By Sleep and where exactly Aqua falls in context. Summarizing Kingdom Hearts in broad strokes is no easy task. If you would rather know more about the games before reading more in detail about Aqua's character, I would suggest visiting the Kingdom Hearts Wiki for more detailed information on the games and main characters.
Kingdom Hearts SeriesKingdom Hearts is a series of video games that focuses on a boy named Sora and those that are connected to him as a result of friendships, encounters and more intricate events. The game is notorious for having strong themes of friendship and the strength of heart, as well as having a variety of interconnected worlds. Characters that wield the power of the Keyblade are able to travel between the worlds and protect them from creatures of darkness such as the Heartless. Various Disney and Square Enix characters make appearances and help Sora and his friends throughout their journeys to defeat the different sources of darkness trying to bring destruction to the worlds. Though the story seems to be simple enough, the plot becomes more and more complex with the release of each new game in the series. An underlying battle between the forces of dark and light is emerging.
Birth By SleepBirth By Sleep is a prequel to the original Kingdom Hearts game, as it takes place years before Sora, Riku and Kairi leave Destiny Islands. It follows the stories of Terra, Ventus and Aqua, a group of friends all training to become Keyblade Masters. The trio is extremely close and believe that nothing would be able to tear them apart. On the day of the Mark of Mastery exam, however, their lives are changed forever. A new darkness threatens the worlds and creatures called the Unversed plague them. Master Xehanort has also gone missing around the time that the Unversed appeared. The three Keyblade wielders are the only ones who can fight the Unversed and set off for different reasons on different paths in order to make things right. Terra, Ventus and Aqua all must struggle with the concepts of darkness and light, understanding their places in the world and changing conceptions of right and wrong. All the while their strong bonds of friendship are tested by doubts, stress and a creeping darkness that threatens to break them apart.
Aqua is the only one of her friends to pass the Mark of Mastery exam and become an official Keyblade Master. She is the first female Keyblade user that we know of and has strong magic abilities. Entrusted by Master Eraqus to bring Ventus home and watch over Terra, Aqua sets off on her own journey. She is somewhat disheartened over the separation of her friends and will do anything to make sure they are safe. Aqua is a main character in Birth by Sleep and has only made minor appearances/been mentioned in Kingdom Hearts II and Dream Drop Distance.