Tatsuemon Yanami is the grandfather of protagonist Hanegi Manami and the inventor of the powered armor suit Delpower X, which he designed specifically for her. The suit arrives via helicopter as the story opens. Tatsuemon engages in a longstanding rivalry with another inventor, Von Getsueru. This conflict escalates when Getsueru's forces, including soldiers called Gernanoids, target both the Delpower X armor and Manami as part of a galactic conquest. Tatsuemon himself pilots the Delpower X armor on one occasion to deliver Manami's forgotten lunch box, becoming pursued by Getsueru during the attempt. Depicted with facial hair and glasses, Tatsuemon demonstrates his capability as a mecha pilot through this operation. His provision of the powered suit to Manami directly instigates the central conflict, leading her to confront threats against her school.