Lea

Lea is the human form of Axel, and a former close friend of Isa, Saïx's human form. He appears in Kingdom Hearts Birth by Sleep as a teenager, alongside Isa, and he returns as an adult in Kingdom Hearts 3D: Dream Drop Distance, in which he chooses to become a Keyblade wielder.

Kingdom Hearts Birth by Sleep
By the time Terra and Aqua had left Radiant Garden, Lea had conspired with his best friend, Isa, to break into Ansem the Wise's castle (for unknown reasons). When walking past the town square, Lea notices Ventus drop his Wooden Keyblade and picks it up, offering to give it back to him. Though Isa tells him they need to hurry, Lea tells him to lighten up since "it will only take a sec". He calls Ventus a kid for "playing" with a wooden "toy" and proudly takes out his frisbees, saying they're real weapons. The two introduce themselves, and then Lea calls for a one-on-one fight, finally prompting a smile from Ventus.

After the battle, an exhausted Lea suggests that he and Ventus call it a draw. Then he calls Isa out for not trying to make up excuses for his loss and cheer him up, causing Ventus and Isa to laugh. He then tells Ventus that they'll meet again someday, because they are now friends. Isa wonders why he keeps "picking up stray puppies", and Lea tells him that he wants to live forever in the memories of everyone he meets. Lea then declares himself immortal after Isa jokes about trying to forget him all the time. After that, Lea and Isa walk off and look up at the castle, apparently 'ready.'

Sometime after Terra-Xehanort is defeated, Lea and Isa are seen being thrown out of the castle by Dilan with Aeleus looking on nearby. Lea later 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 some point in time, Lea and Isa's hearts were consumed by darkness and transformed into Heartless. However, their strong hearts and wills allowed their vessels to continue on as Nobodies. Organization XIII eventually found the pair and named them "Axel" and "Saïx", then inducted them in as Numbers VII and VIII. However, the two had joined the Organization in order to carry out a secret plan to take it over.

At some point, Lea's Heartless was destroyed by Sora, setting the stage for Lea to reform once Axel is destroyed.

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 missing Braig and Isa. After talking with Aeleus, he finds out there is no one else in the Castle or on the castle grounds 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, in which case they reappear in Traverse Town. Lea finds Ansem the Wise's notes about the Door to Darkness, and leaves through a Corridor of Darkness to find the still missing Braig and Isa, complaining that he always gets stuck with the icky jobs.

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 to Mickey and his friends. Lea later joins Mickey, Donald, and Goofy inside the Mysterious Tower and makes a request from Yen Sid that shocks everyone present. Yen Sid warns Lea that the road he has chosen will not be easy, but Lea decides to "jump right in" anyway.

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 Saïx, who have allied themselves with Master Xehanort and become members of his new Organization XIII. Lea briefly fights against Saïx 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 Saïx before he disappears.

Back in the Mysterious Tower, when Riku decides to dive into Sora's dream again to awaken him, Lea tells Riku that he will help out if he should fall into darkness again. In the aftermath of Sora and Riku's Mark of Mastery exam, during which Riku successfully awakens Sora and Yen Sid only names Riku as a Keyblade Master, Lea shocks everybody present by summoning his own Keyblade, claiming that this was the reason he sought out Yen Sid, but has only just mastered summoning it. Shortly afterwards, Lea returns to Radiant Garden.

Appearance
During his youth in Radiant Garden, 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.

After being revived following Axel's demise, Lea wears the black coat he wore during his time as Axel and 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 impromtu 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 while defending Sora, even though he would be using his chakrams against Master Xehanort's Keyblade. Even so, he retains his competitive streak, demonstrated when he states that he intends to compete with Riku in the art of the 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, having received a magically compressed training session from Yen Sid, Merlin and the three fairies.

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.
 * A running gag during Kingdom Hearts 3D: Dream Drop Distance is whenever Lea meets someone from his past, they call him "Axel" and he has to correct them. At the end of the game, when Riku calls him "Axel" again, Lea finally relents.