Hanpei Hattori, nicknamed "Hanpen," is a frugal yet eccentric private detective hired by Mitsuko Komyoji to track the missing android Jiro. A descendant of legendary ninja Hanzō Hattori, he navigates cases in his unreliable green Subaru 360, its frequent mechanical mishaps contrasting his sharp investigative skills. While initially appearing bumbling, he proves adept across multiple missions, partnering with his apprentice Etsuko Sarutobi to counter the rogue organization DARK and its robotic forces.

During a pivotal clash at DARK’s headquarters, he aids in extracting Dr. Komyoji’s brain from Hakaider’s body, ensuring its safe return. Escaping the base’s destruction with Mitsuko and Etsuko, he leaves Jiro’s status unresolved.

His legacy continues in *Kikaider 01*, appearing briefly among survivors in the OVA sequel. A crossover in *The Boy with the Guitar: Kikaider vs. Inazuman* highlights his tenacity—and occasional missteps—when he mistakenly targets high school student Saburo Kazeda as Jiro, sparking a battle between Jiro and Inazuman.

Across the *Kikaider 01* tokusatsu series and spin-offs, he bridges human and android narratives as a recurring figure. The moniker "Hanpen," referencing a fish cake, encapsulates his comedic underdog persona amid larger conflicts.