In the second installment of Uchuu Kaizoku Mito no Daibouken, Aoi, a young man raised on Earth, discovers that he is the heir to the throne of Mito, a former queen who has since become a space pirate. Mito's extraterrestrial species determines gender at puberty, and Aoi must come to terms with his newfound identity while working with Mito and a police officer named Mutsuki. Aoi and Mutsuki develop feelings for each other while evading capture, ultimately joining forces to save the galaxy. Aoi's transformation into a beautiful young woman is a result of this journey. A powerful new enemy threatens the galaxy, and Aoi and Mutsuki must work together to defeat her. As they do so, they become the first royal tandem of queens in the galaxy and make history.