After their homeworld is destroyed, the surviving people of the planet Barm travel to Earth hoping to buy land where they can settle. The negotiations collapse when the Barmian leader, Leon, is killed by his own second in command, Olban, and the Earth delegation is blamed for the murder. In the turmoil that follows, Doctor Isamu Ryuuzaki of the Earth side is shot dead. Soon afterward, Leon's son, Admiral Richter, launches a campaign of terror against Earth, sending a range of mechanical soldiers against its defenses. Humanity's only real protection is Daimos, a transforming super robot that fights with karate, and its pilot, Kazuya Ryuuzaki. Everything shifts when Kazuya falls for a mysterious girl named Erika, who is revealed to be Richter's sister. As the two struggle to be together again, each comes to see that the other side is not wholly evil and that their own side is not wholly good. A mecha drama with a strong romantic core, it closes Tadao Nagahama's Romance Super Robot Trilogy.