Despite his age, Riku is quite mature, and acts somewhat like a mother hen, looking after others.

He looks out for friends and family, he likes to cook, and is adventurous, finding entertainment in the simplest forms such as playing catch and exploring a ship. But, its easy to see he is a child because he dislikes being treated like a kid. He'll even tell people, "I'm not a baby!", especially his older brother Kai who teases him and gets overprotective at times.