A hysterically comical private investigator who befriends Jiro/Kikaider and the Komyoji siblings, assisting them in their crusade against DARK. He is supposedly a descendant of the famous real-life ninja Hanzō Hattori. Hanpei is often derisively nicknamed "Hanpen" by his friends (hanpen is Japanese for "pounded fish cake"), something even Saburo/Hakaider himself is not immune to doing.
Hanpei Hattori is played by Shun Ueda.