Inspector Koichi Zenigata, a dedicated Interpol officer, is assigned to protect two valuable photographic plates connected to the Tokugawa treasure for display at Tokyo's Aquapolis theme park opening. His relentless pursuit focuses on apprehending the thief Lupin III, who constantly targets the plates. A botched high-stakes operation involving the plates causes massive chaos and property damage, leading to Zenigata's suspension from Interpol. He loses his badge, handcuffs, and gun as a consequence. Despite his suspension, Zenigata continues his investigation independently, driven by professional duty and a personal obsession with catching Lupin. During this unsanctioned pursuit, he partners with Maria, a reporter documenting his efforts. Maria actively aids his investigation, while Zenigata develops unreciprocated romantic feelings toward her. Maria, due to her own troubled past, views him only as a father figure, complicating their dynamic. Zenigata's investigation uncovers extensive criminal activities orchestrated by Michael Suzuki, the wealthy Aquapolis owner. Suzuki's operations include illegal genetic engineering experiments to create super-soldiers, specifically targeting Maria for her unique DNA. This revelation shifts Zenigata's mission toward exposing Suzuki. His pursuit forces a temporary, reluctant alliance with Lupin when their goals align against the common Suzuki threat. Their cooperation involves infiltrating Suzuki's facilities and gathering evidence. During the climax, Zenigata confronts Suzuki aboard a cargo plane, battling Suzuki's bodyguards. He later orchestrates Suzuki's arrest by coordinating police forces during a confrontation at Aquapolis, using evidence of the illegal genetic experiments. Throughout these events, Zenigata demonstrates significant physical resilience and combat skill, surviving intense confrontations and navigating perilous scenarios like the plane altercation. His professional integrity remains steadfast; he rejects corruption and adheres to a strict moral code, prioritizing justice even without official authority. The resolution partially restores Zenigata's reputation following Suzuki's arrest, yet he immediately resumes his singular chase of Lupin afterward.