Mitsukuni Hyuga, 54, is the founder and chairman of Tokyo's Hyuga Corporation, spearheading artificial muscle fiber technology. He dedicated his life to the company's economic success, enforcing strict expectations, particularly in raising his son Kotaro. From Kotaro's childhood, Mitsukuni implemented rigorous leadership training, grooming him as successor and ultimately appointing him Project Leader for the powered suits central to Hyuga's future. Mitsukuni's driving ambition is completing the Marishi Machina powered suit project to dominate the emerging global market.

His actions critically shape other characters' lives. He reveals to Dan Amo that Dan's mother survives, directing Dan and Makina Mikage to Hyuga's secret Mount Fuji testing facility. Mitsukuni suggests re-conducting a past test performed by their parents' development team might provide answers about their parents' fates and fulfill Dan's desire to revive his mother and Makina's search for her father's true intentions. This manipulation serves his corporate goal of finalizing the Marishi Machina suit. After a critical Shutoko expressway incident involving the suit's control over Makina, he intercepts Dan and Makina, presenting Dan with an unexpected order instead of punishment for involving Kotaro. Mitsukuni was involved in the past incident that claimed the lives of Dan and Makina's parents, directly connecting him to their unresolved traumas.