The protagonist is trying to go straight even as rival gangsters try to kill him and refuse to follow the Yakuza code.  
The title character is married to a nightclub singer and sings and whistles throughout the film.  The villain wears bright red shirts and an outlandish moustache.  The protagonist is trying to go straight even as rival gangsters try to kill him and refuse to follow the Yakuza code.  FTP, name this 1966 Seijun Suzuki movie, whose protagonist cannot stay put within a certain Japanese city.
The title character is married to a nightclub singer and sings and whistles throughout the film.  
Tokyo Drifter or Tokyo Nagaremono or The Man From Tokyo