Commander Sugata is a scientist and sage who excels in mental reinforcements and is a master of every martial art. He discovered the existence of the Underground Empire Tube, a once peaceful kingdom that has turned into a malignant force under the mysterious Zeba, who desires to conquer the surface. In order to stand against them and thwart their plans, Sugata recruits five young people to become the Maskmen. Each becomes specialized in a style of martial arts, and Sugata teaches them the ways of the mystical "Aura Power" energy. A year after Sugata recruits and trains the Maskmen, the Underground Empire Tube is ready to strike. Princess Ial of the deposed Igam Royal Family, sent to spy above ground as Mio, falls in love with Takeru, and wishes for those underground and above ground to coexist. She is kidnapped and imprisoned in ice for her betrayal. As Takeru and the Maskmen battle Tube, they learn about Ial and Igam's relationship, and a terrible dark secret about Zeba, the Tube leader.