Gyangu tai G-men

Gang vs. G-Men is a 1962 Japanese color crime thriller film directed by Kinji Fukasaku starring Kōji Tsuruta, Shinichi Chiba, and Tetsurō Tamba. In an interview with Chris Desjardins contained in the book Outlaw Masters of Japanese Film, Fukasaku called the film "the story of an ex-yakuza who becomes an undercover policeman."

Synopsis from Wikipedia, CC BY-SA 4.0. Everything below written here.