Under the rule of Emperor Fuburai, Mahu, who came from another dimension, plotted to conquer the galaxy. Their schemes were repeatedly thwarted by space detective Jyder and his ally Lenny. After their invasion plan on Earth failed, Priest Bora sought a final resolution. His plot involved firing a beam cannon powered by all of Unon Castle's energy, destroying Jyder's mother ship. As a result, Jyder lost his ability to transform and was forced to return to the Galactic Patrol Headquarters. Facing the reality that repairs would take 421 hours, Earth's defense was left solely to Lenny. The enemy's Unon Castle, located within an active volcano, became the site of intense battle—ultimately leading to Lenny's capture.