|Affiliation||Space Science Laboratory|
|Family and Relations||Unnamed Parents,|
Duke was the crown prince of Planet Fleed spending his childhood with friends like Nadia and her brother Sirius. However, one day the Vegan Empire attacked the peaceful planet. Duke was sent out into space with the Grendizer to a distant planet. Upon landing on Earth, Duke meets the scientist Genzo Umon who used Duke's concussion to convince him that he was the doctor's son to protect him from threats.
Duke has a much different design than his counterpart having a slimmer build and a significantly different hairstyle that is slightly similar to Koji's. In his pilot suit, Duke is identical to his original counterpart.
Duke is generally easy going and polite but is tough and fearless towards enemies and rivals. He loves and respects Dr. Umon for taking him in and gets along well with Hikaru Makiba and her family. He has a strong bond with Koji Kabuto even though they argue a bit and Duke is against the idea of his sister liking Koji. However in spite of the closeness he has with the people on Earth, he feels alone on an alien world with some relief the revelation that Maria Fleed had survived. Duke wishes to preserve the honor and dignity of Planet Fleed, striking down the Empire for attacking it and destroying an underground city that had ties to it on Earth.
When Duke discovers that Dr. Umon had been investigating the artifacts from the sight he previously destroyed, Duke begins to lose his patience with humanity. By the time the government began to speak doubts about the Grendizer, Duke was provoked to rule over Earth in order to protect the planet from both the Vegan Empire and themselves. It was only the words from his friends that prevented Duke from doing so before an all-out war broke between Grendizer, the Vegan Empire, and Earth's government.
Duke spent a good part of his life as Daisuke Umon working on the ranch of Danbei Makiba, a friend of his father. He had a rather carefree life until Koji Kabuto came in on the TFO and revealed something about UFOs. While Duke was regaining his memories, Dr. Umon tried to prevent it from happening until his memories fully resurface and Duke goes to rescue Koji on the Grendizer. Ever since, Duke fought against the Empire while trying to avoid its attempts to take his life and revealing a dark secret about the Saucer Beasts from the mind controlled Nadia. Soon Duke makes a small but uneasy alliance with the Mycenae Empire. It ended during an attack by the Vegan Empire when Koji in a state of mixed emotion dropped the casing of the Emperor of Darkness. Trapped within the underground ruins, Duke tries to find a way out eventually finding a wormhole that drops him and the Grendizer near the sun which gives the Grendizer enough power to escape and get everyone to the surface. When Koji reveals a hidden city, Duke destroys it recognizing the technology to be like Planet Fleed's.
Soon Duke reunites with his sister Maria after clearing up a misunderstanding. However Duke also finds that Dr. Umon had been studying artifacts from the destroyed city. When confronted by Dr. Umon, Duke reveals that he knew of a connection between that city and Planet Fleed and destroyed it because he was concerned that the people of Earth would think that Planet Fleed would be filled with invaders. With the government on high alert and losing faith in the Grendizer as it was an alien robot, Duke resolves to rule the planet himself. However, Koji and the others try to talk him out it. By the time Earth's armies and the Empire begin to exchange blows, Grendizer's inspiration Great Spirit Raaga also joins the battle. Sayaka helps fight the Vega Beasts but keeps Duke on a short leash. But by the time nuclear war broke out, Raaga's programming kicked in and dove into the Earth. Duke and Maria pursued it with Grendizer and Drill Spazer but Raaga unleashed a shockwave that caused an earthquake and tsunami that wiped out civilization. Duke had then entered stasis after Grendizer went into a hibernation.