Gi Koyuu is a character in Seiran Den, and Nakago's biological father. He is the Shogun of Kuto’s army until Nakago takes over. He and Nakago’s mother, Matuta, met when Koyuu was injured from a battle and Matuta found him and dressed his wound. The two fell in love and Nakago was the product of their passion. While Matuta and Koyuu still longed for each other after that, they were forbidden to be together since Matuta is a member of the Hin race.