Koichi Zenigata is an Interpol inspector from Japan and the central law-enforcement adversary in The Mystery of Mamo. He is a descendant of the legendary fictional detective Heiji Zenigata, a lineage that underscores his deep-seated commitment to justice. In this film, Zenigata is depicted in his earlier, most intense form, embodying a personality that is obsessive, hot-tempered, and relentlessly driven. His demeanor is far from the more comedic and sentimental figure he becomes in later series; here, he is dangerously focused and displays a near-unhinged dedication to his mission. His singular motivation is the capture of master thief Arsene Lupin the Third, a goal that consumes his entire identity and overrides all other personal and professional obligations. This is powerfully demonstrated when his superiors order him to abandon the Lupin case. Rather than comply, Zenigata immediately resigns from the police force on the spot, declaring his intent to continue the pursuit as a private citizen. This act of defiance represents a significant moment of development for the character, showing that his personal crusade has become more important than the institutional authority he represents. His role in the story is to serve as the persistent and righteous foil to Lupin, representing the forces of order in a world of chaos. His key relationship is entirely centered on Lupin, whom he views as his ultimate rival and the singular target of his life's work. While purely adversarial in this narrative, the intense, personal nature of the chase establishes the foundation for the grudging respect that would later define their dynamic. The film also touches on his personal background by briefly mentioning he has a daughter named Toshiko, a detail that is unique to this movie and highlights the personal sacrifices his obsession demands. In terms of notable abilities, Zenigata is a highly capable detective whose tracking skills are formidable enough to pursue Lupin anywhere in the world. He is also physically adept, proficient in hand-to-hand combat and skilled with a firearm. Despite his frequent failures to make an arrest, his sheer tenacity and resourcefulness make him a constant and formidable threat.