An employee of Museum, Kirihiko was given a Gaia Driver and the gold Nasca Memory to become the Nasca Dopant. He also became engaged to Saeko Sonozaki and assisted her in her job of dealing Gaia Memories while using the Digal Corporation as a front.
Sudo oversaw the distribution of Gaia Memories and fought Double whenever he interfered, coming to see him as a rival. However, after learning of the true goals Museum from Ryubee Sonozaki, Kirihiko defects from Museum and helps Double defeat the Bird Dopant. He attempts to convince Saeko to leave with him but instead she kills him and snatches the Nasca Memory.
Kirihiko's death would later spur his sister Yukie Sudo to come seek revenge on his murderer.