He is another keyblade wielder and has power over darkness and light. He is Sora's best friend. In the first game he's in, Kingdom Hearts 1, Maleficent puts powers of the dark in him. You have to fight him in the end of kh1. In kh2 he is your friend. but this is kh1 riku not kh2 riku so lets not talk about him then, ok? Peace Out.