This has a similar look to some of the early 70s New York gangster and Blaxploitation flicks, only with an eye for the big moody shadows that wouldn't be out of place in a Carol Reed movie. The acting is pretty good, even when the hero is tired and emotional, and the few characters that are fleshed out are never let down by the script. It's easy to see how Riki Takeuchi and Takashi Miike misspent their youth. I wouldn't go so far as to call it a classic, but it compares very favourably with the the best of its era.
The twang of the jaws harp and the jarring off-key harmonica are a nod in the direction of Ennio Morricone. The hyper realism (and melodrama)is very much of its day. Think of Larry Cohen, Sergio Leone, Roman Polanski, Sergio Corbucci, Sam Fuller, Sam Peckinpah, Don Siegel, and their ilk in the 60s and 70s, and accept that film has always been an international conspiracy by artists with attitude. Audiences may be isolated by language, but filmmakers are interested in the visual aspects, and they don't need translation, only an understanding of technique. Kurosawa and Mishima opened up Japanese cinema to the world, and Japanese film makers responded by drawing influences from the wider world.
This movie takes the technical influences and extrapolates them into the boom years of the Japanese economy. Where's there's money, there's organised crime. The casual unaffiliated street punk was a dying breed in the 70s. It's noticeable that the "punks" don't wear suits. They look more like refugees from the beatnik era, and the jazzy sections of the score (that accompany their drunken good times) seem to be saying that their day is done. Kinji Fukasaku is as deserving of credit as any of the aforementioned masters of pulp. His eye is true, and whenever he has a decent script, he makes a good or a great movie, usually on a tight budget. Who could ask for more?