Proof of the Man (1977)

Jonny Hayward, a black American, travels to Japan, but is murdered there. Detective Munusue is one of the team of detectives investigating the killing. Munusue begins to suspect that rising fashion designer Kyoko Yasugi may have either information or actual involvement in the murder. When Yasugi's son Kyohei flees to America after a hit-and-run killing, Detective Munusue goes to New York and teams up uncomfortably with NYPD detective Ken Shuftan to find Kyohei and to get information from Jonny Hayward's father, who was stationed in Japan after the war. Munusue, whose father was beaten to death by American G.I.s when the detective was a boy, must confront his own vengeful antagonism to former U.S. soldiers in order to solve the case.