Lea

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.

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. 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.