Riku only makes a short cameo at the end with literally one line, but since this is a long term project you can choose to continue the role in KH1 onward.

Riku is a calm, cool, collected teenager who is not afraid to push the boundaries. This is illustrated by his lack of fear while stepping into the dark portal during Destiny Islands' demise. His exclamation of, "I'm not afraid of the darkness!", furthers illustrates this point.

During Kingdom Hearts in particular, Riku has a strong competitive streak. He shows his competitive side when he challenges Sora, saying that his heart is stronger than his friend's. Due to the influence that Maleficent has on him, Riku also becomes increasingly jealous of Sora.

Voice type: https://www.youtube.com/watch?v=Z4JYGIKS0sM