High School DxD Novel Volume 6 was written by Ichiei Ishibumi and features illustrations by Miyama-Zero.

Years ago, Asia healed the wounds of a demon by using her Sacred Gear. When the Church learned of it, she was excommunicated from the organization that had been her entire world. Now, that same demon, Diodora, has returned, hoping to marry Asia. Only defeat in a Rating Game can stop him, but could there be more to the gentle-looking demon Asia rescued from death than first believed?