An early Teruo Ishii film. It was released just 5 years after his debut, though he already had 20+ films behind his name by then. People expecting vintage Ishii (i.e. the edgier films he's best known far) will be a little disappointed, Gang vs Gang is a pretty standard crime flick, albeit with a cooler ending.
Mizuhara served five years in jail to protect his boss. On the day he is released, his car is shot to shreds. Mizuhara discovers his former gang is behind the attack, clearly trying to get rid of any loose threads. He also learns his old boss is dealing drugs for a living, which gives him a good idea for revenge.
Gang vs Gang is a pretty basic Japanese noir, sporting sullen men in long coats and hats, doing shady business in lively bars. The first hour is a little slow, very dialogue-driven and not all that exciting, the final 30 minutes is a lot more fun, with some welcome action in a somewhat surprising setting. Not terrible, but I prefer Ishii's more extravagant films.