Riku is a main character and he lives on the same island as Sora and Kairi, but he falls into the path of evil through Malificent.
Riku appears as a vague antagonist just like in the game but starts off as a good friend to Sora and Kairi, after Darkside destroys Destiny Islands
Riku ends up sided with Malificent. As part of Malificents group he has been ordered to retrieve Pinnochio from Monstro.
His best friend is Sora. Out of the two, Riku is shown to be the straighter of the two. He hates when Sora touches him, and tries to ignore his homosexual remarks. However, Riku is shown to be gay himself, where is crush is Sora, as shown in Episode 8. He also hates when people spell Auron wrong.
Riku lives on the Destiny Islands with Sora and Kairi, but they want to escape on a raft, until the Island is taken over and destroyed by the Heartless. Riku is taken by Malificent and agrees to work with her.