Rikuo is not an average 13-year old boy, his mother is Nura Wakana and he inherited 1/4 of his grandfather's youkai blood. In times of impending danger his youkai blood awakens and he switches into his night form to become the the Master of the Youkai(The master of all spirits). Destined to take over as The Third Master of Youkai from his grandfather. Rikuo once embraced the idea and played pranks on the other Youkai, but after realizing the evil nature of the youkai deeds he rejects the idea of becoming their master. He attempts to become more like a normal human by doing all sorts of good deeds, but he still appreciates his youkai underlings. After being tested by Gyuuki he decides to take the position of Young Head and saves both humans and Youkai.
He is seemingly weak but very clever, easily manipulating one of the council members into isolating himself during a meeting and rationalizing against the dissolvement of the Gyuuki Group. He can only transform at night or in darkness and reverts to normal in sunlight. Originally he couldn't remember things he did as his "Night" form, but he later is able to see and communicate with him. Together they plan to form a "Hyakki Yakō" of their own.