Aqua

Aqua is one of the main protagonists in Kingdom Hearts Birth by Sleep, and the main protagonist of Kingdom Hearts 0.2 Birth by Sleep - A Fragmentary passage, she also appears in Kingdom Hearts III. She is one of the Keyblade Wielders before Sora. Like Terra and Ventus, it's her dream to become a Keyblade Master. She is the only one out of the three to achieve that goal and earn the title of 'Keyblade Master'.

Her name is Latin for "water", while Kairi's name in Japanese means "sea". The only connection between the two is that Aqua met Kairi in Radiant Garden in Kingdom Hearts Birth by Sleep and put a protective spell on her necklace, which later brought Kairi to Destiny Islands. Kairi, by accidentally touching Aqua's Keyblade during this time, also inherited the Keyblade from Aqua. The official Japanese website refers to Aqua as the "Dancing Waters Forming Bonds" (絆繋ぐ舞水 Kizuna Tsunagu Busui?).