once upon a time there was an ordanary boy named sora who was friends with his two friends who's names were Riku and Kairi. Sora always felt left out because he was younger than Riku and Riku was better than him and sence Kairi was a girl and highly respected sora earned the title of a non-capitalized name unless in the beginning of a sentince so no body was aloud to yell out sora's name or else that would capitalize every letter and cause dispair and pain to all.
so on day a door opened and some things happened that created little bug shaped shadows that attacked people trying to steal the darkness in their hearts and hurting folks while doing it and eventually ruling the world by going into a giant keyhole through the door they passed on their way to distruction of the planet which was called Destiny Islands but nobody cared cause it was a small hardly populated area so nobody knew about it therefor creating loss in words and eventual dying for no apperent reason.
Sora became the keyblade master, a boy who swung around a giant key called a keyblade hence the title keyblade master and it was called a keyblade cause of it's appearance in the real and non-real world and dimension and it's use in the fabric of space.
Sora killed Riku and saved the world.