Stray Dog (1949) is an Akira Kurosawa buddy-cop Japanese film noir undercover heatwave detective police procedural homicide back-street illicit arms market absolute classic of Japanese noir, that stars Toshiro Mifune and Takashi Shimura.
It was Kurosawa's second film of 1949 produced by the Film Art Association and released by Shintoho and while considered a noir, it should also be fully considered as a fully formed detective movie and indeed you should know it as being among the earliest films in that genre.