Isa

Isa is the complete being of Saïx, and is a close friend of Axel's complete being Lea. He appears in Kingdom Hearts Birth by Sleep as a teenager, alongside Lea.

Kingdom Hearts Birth by Sleep
At some point during Kingdom Hearts Birth by Sleep, he has a conversation with Ventus, along with Lea.

Descent into Darkness
At an unknown point in time, his heart was consumed by darkness, turning him into a Heartless. However, his strong will gave him the ability to continue on as a Nobody: Saïx. Some time later, Organization XIII found his Nobody, who received the name Saïx and was inducted into their ranks as Number VII. It is known that he joined alongside Axel, and the two had a secret, unknown plan.

Appearance
Isa appeared in a recent trailer for Kingdom Hearts Birth by Sleep. He wears a short-sleeved, navy blue jacket with a light blue stripe going along his shoulders to the ends of his sleeves. The jacket's collar is rather high and is sky blue, as are the ends of the sleeves and the bottom hem of the jacket. There is a yellow crescent moon symbol prominently displayed on the left breast of the jacket, referencing Saïx's attribute in Organization XIII.

Isa appears to wear a black undershirt, as well as white pants and black shoes. He looks about the same age as Ventus. His hair resembles his Nobody's style, but shorter, Isa's being slightly longer than jaw-length. Like with Lea, Isa's hair is spiked slightly upward. He lacks Saïx's X-shaped scar, and has green eyes rather than yellow. His ears do not appear to be pointed like Saïx's either.

Personality
Like his Nobody Saïx, Isa is much quieter than his companion, Lea, with a similar speaking tone. He has no interest in fighting on Lea's side in a childish challenge, but is shown smiling as Lea and Ven fight. He is shown having a more care-free personality compared to his Nobody and values his friendship with Lea.

Trivia

 * "Isa" is a name in both Arabic and Sanskrit.
 * The differences between Isa and his Nobody Saïx in physical appearance (with the exception of the latter's scar) indicate that Isa would at one point wield darkness even before producing a Heartless.