Sora

Sora is the main protagonist in almost all of the Kingdom Hearts games to date and the wielder of the Keyblade, the Kingdom Key. His strong sense of justice and immense power makes him a near-perfect hero.

Biography:
He, Riku, and Kairi were living on Destiny Islands until he and his two friends wished to see what other lands there were. When the Heartless invaded, Kairi, Riku, and him were driven into a cave where they were then driven into an unknown world. After finding out from his Disney friends what the Heartless were doing, he was given the Kingdom Key and began to fight the Heartless.

Kingdom Hearts: Lost Cause
In the prologue as an NPC and re-incarnated into Oxus.

Kingdom Hearts: Tears of Destiny
In Tears of Destiny, Sora appears in the prologue. A strange wind blows through Destiny Islands and he, Kairi, and Riku are transported to the world of Crystal Isles. He is separated from Kairi and Riku and he encounters a giant Heartles, Crystal Behemoth. He atempts to fight it, but is killed. Later, Roxas wakes up, and Sora's body had become Roxas as Sora was no longer in his body.

Later, Maleficent is bargaining with Hades. She wants Sora's soul so she can use the power of the Key Blade. It is revealed that she had sent the Heartless after Sora to turn him into a Heartless, but it had ended up killing him instead. Roxas and Kairi then comes to the Underworld, and Sora's soul is liberated. His soul, having nowhere to go as his body is being inhbited by Roxas, posseses Kairi. Both Sora's and Kairi's conciousnesses are in her body, though she is in control of it still. Roxas and Kairi/Sora then continue the quest to defeat Organization XIII. At the end of the game, after Roxas has become whole, he goes back to his own body. Him and Kairi then return to Destiny Islands, believing Riku to be dead.