As a private investigator in Tokyo, Ryo Saeba (also known as the City Hunter) joins forces with his partner, Kaori Makimura, to assist actress Emi Makaze in finding her lost sibling. However, they soon discover that her brother is actually a delusional ex-soldier named "The Professor," who seeks to destroy Shinjuku district. With Kaori responsible for Emi's safety, they both become entangled in The Professor's plan. The City Hunter is now tasked with saving them and stopping the annihilation of downtown Tokyo.