Lea is the original persona of Axel, and a close friend of Isa, Saïx's original persona. He appears in Kingdom Hearts Birth by Sleep, as a teenager, alongside Isa. After the destruction of Axel and his Heartless, Lea is reborn as an adult with the memories of his time as a Nobody intact. He later gains the abilities to use a Keyblade.
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 takes out his frisbees. Ventus, not seeing them as much better of a weapon than his wooden Keyblade, calls them lame. The two introduce themselves, and then Lea calls for a one-on-one fight, finally prompting a smile.
After the battle, Lea calls Isa out for not trying to make up excuses for his loss and complains that he should've chosen Ventus for a best friend rather than Isa, 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.'
In the ending credits, 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 will give him the ability to continue on as a Nobody: Axel. Sometime 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
Following the destruction of his Heartless and Axel's suicide, Lea awakens in Ansem the Wise's computer room to find that he is a complete being once again. While Ienzo and Aeleus have Dilan and Even rest to recover from their resurrection, Lea sends his time searching Radiant Garden for Xehanort, Braig and Isa. Finding Ienzo and Aeleus rummaging around Ansem's old study, Lea wonders if they could have come back into existence somewhere else. However, Ienzo tells him that when someone's Nobody and Heartless are destroyed, the person they come from is reborn at the very same spot they split from in the first place. Lea decides to search the worlds for Isa, saying he's always stuck with the icky jobs.
While traveling, Lea arrives in Disney Castle and fends off a blast of magic from Maleficent via his chakrams and scares Pete with the other one, allowing Queen Minnie to free herself from him. Once the two villains leave, Lea reveals himself to Mickey, Minnie, Donald and Goofy, and introduces himself.
He then goes with them back to Yen Sid's tower, where he requests to become a Keyblade wielder to help Sora/Roxas. Despite Yen Sid warning it would not be an easy path to take, Lea remains adamant about it. He then spends a compressed training session (training a long time, but in reality it takes place in a short amount of time) thanks to the magic of Merlin, Flora, Fauna and Merry Weather.
When Lea receives word that Sora has been captured by Master Xehanort and is in danger of becoming the thirteenth vessel for a fragment of his heart, Lea leaves his training and, despite not being able to materialize a Keyblade yet, rushes off to the Realm of Sleep to save Sora along with the help of Mickey, Riku, Goofy and Donald. Much to his shock, Lea finds Isa still sides with Xehanort and is now becoming one of his twelve clones.
Once Riku saves Sora's heart from the darkness and Ventus's possessed armor, Lea tries materializing his Keyblade again and succeeds, promising that he will help them in the coming battle against Master Xehanort. He later then returned to Radiant Garden.
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 widow's peak, 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 keffiyeh 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, the sole difference being the absence of the teardrop marks on his face.