If you return kindness with hostility, you'll regret it.
In the first five minutes of 1967's Massacre Gun, a yakuza boss sends out his most trusted underling to eliminate his former mistress, who has left him for another man. The rub is the other man is the boss's underling, who's conflicted but goes through with it anyway because orders are orders, even when they involve the woman you love. This is how the viewer is introduced to Ryûichi Kuroda (Nikkatsu superstar Jô Shishido), whose loyalty is split between his criminal family, headed up by the fatherly Akazawa (Takashi Kanda), and his actual family, represented by his younger brothers Eiji (Tatsuya Fuji) and Saburo (Jirô Okazaki), with whom he runs a swanky nightclub. Hotheaded middle brother Eiji is just as entrenched in Akazawa's gang as Ryûichi is, but the youngest, Saburo, who plays drums in their club's jazz band, is being groomed for a career as a professional boxer. That goes by the wayside, though, when he tells Akazawa off, vowing to make it without the boss's support, and has his hands smashed in retribution. This, in turn, prompts Ryûichi to tender his resignation, precipitating an all-out gang war that leaves few gangsters standing at the end of it.
Co-written and directed by Seijun Suzuki protege Yasuharu Hasebe, Massacre Gun is a remarkably assured work for someone who made his debut just one year earlier (with the evocatively titled Black Tight Killers). Not only is it chock full of striking compositions and fluid action scenes, it also gives Ryûichi a formidable foil in the form of his old friend Shirasaka (Hideaki Nitani), now Akazawa's heir apparent, who fruitlessly tries to stay out of his line of fire. Once things pass the point of no return, though -- you can take your pick, but I'm partial to the moment where the Akazawa gang delivers one of the Kurodas' allies to their club in a coffin loaded with dynamite -- there's no chance of escape for anyone.