The third installment of Tadao Nagahama's Romance Super Robot Trilogy. (Volume One: Chou Denji Robo Combattler V, Volume Two: Chou Denji Machine Voltes V)
Following the annihilation of their home world, the survivors from the planet Barm head toward Earth, hoping to negotiate the purchase of land for emigration. However, during the talks, the Barmian leader, Leon, is murdered by his second-in-command, Olban, and the Earth delegation is framed for the killing. In the resulting turmoil, Doctor Isamu Ryuuzaki, a member of the Earth delegation, is shot and dies.
Shortly after the negotiations collapse in disaster, the Barmians (referred to as "Valerians" in Starbirds) launch a terror campaign against Earth, led by Leon's son, Admiral Richter, who unleashes a variety of "Mecha Soldiers" against the planet's defenses. The only barrier between humanity and total destruction is the transforming, karate-wielding super robot Daimos and its pilot, Kazuya Ryuuzaki. But everything changes when he meets and falls in love with a mysterious girl named Erika, who turns out to be Richter's sister. Throughout their efforts to be reunited, Kazuya and Erika each come to realize that the other's people are not entirely evil—and that their own people are not entirely good.