Lea

Lea is the original persona of Axel, and a former close friend of Isa, Saïx's original persona. He appears in Kingdom Hearts Birth by Sleep as a teenager, alongside Isa, and returns as an adult in Kingdom Hearts 3D: Dream Drop Distance.

Kingdom Hearts Birth by Sleep
While Ventus is in the Radiant Garden, Lea walks by, picking up the Wooden Keyblade from the ground. He asks Ventus if it's his. When Ventus responds that it is, Lea calls him a baby for "playing" with it and proudly takes out his frisbees. The two introduce themselves, and then Lea calls for a one-on-one fight, finally prompting a smile from Ventus.

After the battle, Lea calls Isa out for not trying to make up excuses for his loss causing Ventus and Isa to laugh. He then states that they'll meet again someday, because he and Ventus are now friends. After that, Lea and Isa walk off and look up at the castle, apparently 'ready.'

Sometime after Terra-Xehanort is defeated, Lea and Isa's plan is revealed, as both were seen being thrown out of the castle by Dilan with Aeleus looking on nearby. In the next scene, Lea buys sea-salt ice cream from Scrooge McDuck and gives one to Isa as they stare up into the sky.

Between Kingdom Hearts Birth by Sleep and Kingdom Hearts 358/2 Days
At an unknown point in time, Lea's heart was consumed by darkness, turning him into a Heartless. However, his strong heart and will gave him the ability to continue on as a Nobody: Axel. Some time later, Organization XIII found his Nobody, who received the name Axel and was inducted into their ranks as Number VIII. It is known that he joined alongside Isa, and the two had a secret, unknown plan.

Kingdom Hearts 3D: Dream Drop Distance
After Axel sacrifices himself to give Sora safe passage to the World That Never Was, Lea awakens in Radiant Garden, with his memories of his time as Axel intact. Discovering that four of the founding members of Organization XIII, Aeleus, Even, Dilan and Ienzo, have been reborn as well, Lea decides to look around for the others. After talking with Aeleus, he finds out there is no one else in the Castle and Ienzo explains that when someone is reborn after losing their heart, they appear in the same place where they lost it, unless their world disappeared. Soon after, Lea leaves through a Corridor of Darkness to find the still missing Braig and Isa.

Lea's travels eventually bring him to Disney Castle, where Maleficent and Pete are holding Queen Minnie hostage against Mickey, Donald, and Goofy inside the castle library. Lea discreetly uses his chakrams to block Maleficent's attack and surprise Pete long enough for Minnie to escape from his clutches, and once Maleficent and Pete are gone, Lea introduces himself. Lea later joins Mickey, Donald and Goofy inside the Mysterious Tower and makes a request from Yen Sid that shocks everyone present.

Lea later arrives just in time in The World That Never Was to aid Riku and Mickey in saving Sora from becoming Master Xehanort's final vessel, in the process finding Xigbar and Isa, who has allied himself with Master Xehanort and become a member of his new Organization XIII. Lea briefly fights against Isa to defend Sora, and manages to knock him away just as Donald and Goofy arrive. Master Xehanort, knowing he cannot win now, reluctantly retreats with his men, and Lea shares a final look with Isa before he disappears.

In the aftermath of Sora and Riku's Mark of Mastery exam, during which Yen Sid only names Riku as a Keyblade Master, Lea shocks everybody present, including himself, by summoning his own Keyblade and jokingly states tha he intends to compete with Riku. Shortly afterwards, Lea returns to Radiant Garden.

Appearance
In Kingdom Hearts Birth by Sleep, Lea looks about the same age as Ventus. His hair resembles his Nobody's, but shorter and with the spikes styled upward. Lea has a slight, a trait he also shares with Axel, though Lea's is more noticeable. Lea's eyes are also more of a blue/green color than Axel's striking green. He wears a sleeveless orange jacket with a white, sleeveless shirt underneath, and tan, baggy pants with red and white sneakers and black socks. The pockets of his jacket are a much darker shade of orange than the rest of it. He also wears a yellow and brown around his neck. The pattern of this keffiyeh changes abruptly near Lea's neck, from stripes to a very organized checkerboard pattern. Similar to Braig's scarf, the tip of Lea's keffiyeh is frayed slightly. He bears a curious resemblance to Hayner.

In Kingdom Hearts 3D: Dream Drop Distance, Lea wears the Black coat he wore during his time as Axel and overall appears identical to his former Nobody, only lacking the tear-shaped markings below his eyes.

Personality
Lea is both childish and competitive, willing to disrupt Isa's schedule for his fight with Ventus. This is also evident during the ending credits when he is seen trying to escape from Dilan's grasp by flailing around his limbs, unlike Isa, who realized they couldn't escape and barely moved. He is also somewhat smug and sarcastic just as Axel was.

He wishes for everyone he ever meets to remember him, so he can live on forever through people's memories. Like his Nobody, he uses the phrase "Got it memorized?" on multiple occasions.

As an adult, retaining his memories as Axel, Lea becomes as cocky as his Nobody counterpart, to the point that he actually challenges Master Xehanort to a duel while defending Sora, even though he would be using his chakrams against Master Xehanort's Keyblade.

Abilities
As a teenager, Lea is not physically shown fighting, though he has an offscreen spar with Ventus and loses. His weapons during that time consist of two red frisbees with black edges, each adorned with a Bomb design, which later influence his choice of weapons in the Organization: chakrams.

Upon reaching adulthood following his Nobody and Heartless's destruction, Lea wields the fire-controlling Chakrams once used by Axel, and after Sora and Riku's Mark of Mastery exam comes to an end, he reveals his ability to wield a Keyblade that bears features from the Bond of Flame and Frolic Flame Keyblades.

Trivia

 * In an issue of Famitsu PSP+PS3, Lea's name is misspelled "Lia". It was also once misspelled on the Kingdom Hearts Birth by Sleep official website, though it was later corrected.
 * Although it was a joke, Lea's statement that he should have been friends with Ventus rather than with Isa foreshadows future events. In the future, his Nobody would choose to become friends with Roxas rather than stay friends with Saïx, Isa's Nobody.