The genius of Tokyo Fist is that it's not actually a "boxing film", in the same way all good movies unthinkingly dropped into a category like that claw their way out of the category. Its first third or so sets us up for something we think we can see coming a mile off: a ninety-eight-pound weakling gets sand kicked in his face and has his girl stolen by some muscleheaded bully, and so the weakling goes to the gym, bulks up, clobbers the bully in a fair fight, gets the girl back, and keeps his gym membership too. But then director Shinya Tsukamoto (who also stars as said weakling) yanks the rug out from under us not just once but multiple times. This isn't a movie about men proving their strength, but discovering the depths of their weakness and frailty, and with a feminist angle that not only turns the tables but flips them entirely.
The boxer, the salaryman, and Hizuru
Tsuda (Tsukamoto) hustles through the sweltering cement-scapes of modern Tokyo, hustling insurance to hole-in-the-wall businesses and families. He has a beautiful fianceé, Hizuru (Kaori Fujii, Swallowtail Butterfly), but the emasculating nature of his job leaves him too wrung out to savor the good things. He's the epitome of the bow-and-scrape salaryman, and he knows it. When his boss unctuously asks him to do a favor for a pal, the owner of a boxing gym, Tsuda knows he has no choice, and so he hustles over there. The luridness of the gym wraps around Tsuda like one of Dante's circles of Hell: he's simultaneously fascinated and repulsed by the stink of the sweat and the boxers' pulpy, battered faces.
Someone at the gym recognizes Tsuda. It's Kojima, a friend from his school days. Tsuda doesn't seem interested in getting caught up with an old chum, though — maybe because work is eating his time, or because his father on death's door in the hospital has him and his wife uneasy. But Kojima insinuates himself into Tsuda's life, specifically to make a play for Hizuru. It doesn't matter that Hizuru is perfectly capable of giving Kojima a stare-down all on her own; Tsuda is instinctively possessive — so much so that he can't even stand the sight of her posing for a photo in her company's magazine. Under it all, Tsuda sees her as property, not even a wife or a partner. (He's also already capable of violence, as when he smashes in the wall next to her head after Kojima makes an unannounced visit.)
One night, after Kojima teases Tsuda over the phone about how "very soft" his wife's body is, Tsuda storms over to the other man's apartment and gets beaten senseless for his trouble. If you are thinking this is the trigger that causes Tsuda to head to the gym and start training relentlessly to eventually beat Kojima, you are only half right. In fact, before that ever happens, Tsukamoto shows how the main impact of this incident is with Hizuru. When she sees her husband-to-be battered senseless, it awakens in her the urge to explore just how much her own body can take — the better to declare her independence of not just her husband, but both men.
How this manifests, and the way it occupies a significant portion of the movie, may throw people off, but again that is the idea. The movie sees Hizuru as the character with the most agency in the story, and it's her decisions that drive most of the goings-on. When she moves out of Tsuda's place and into Kojima's, it's not because she wants to offer herself to Kojima; it functions as a thumb in the eye of both men. She's rejecting her fiancé, since he's outed himself as grasping and sexually retrograde — and she's grinding a heel in Kojima's psyche by not making herself available to him. In fact, Kojima turns out to be a cowardly figure, more capable of beating on people outside the ring than inside it.
You can't punch your way out of this one
It's bad enough that both men have toxically masculine personalities, but the movie shows how this three-way tension is just the latest incarnation of something they've both had for a long time. At about the halfway mark, we learn about the uneasy bond they share: once, when still in school, they witnessed a girl being killed by a gang of other boys, and were powerless to do anything about it. They weren't "man enough" then to save her, and now they find they're not "man enough" to one-up each other or either win Hizuru back or win her over. (This only works if one's definition of "man enough" encompasses only physical strength and ignorance of pain.)
Most films with these ingredients would build towards a climax where Tsuda redeems himself by beating (literally) Kojima and winning Hizuru back. What we do get is the two of them facing off, but more out of mutual self-destruction than any aspiration. It's Hizuru who fares better than either of them, even when pushing the limits of her own body with scarifications and tattoos — both done as much to enter realms even the other two men won't approach as it is to push them away.
The first movie I ever remember watching where boxing was a major story element was Martin Scorsese's Raging Bull. Nothing about the sport was glamorous in that film: half the time it felt like the camera itself was being beaten up. Tokyo Fist's stylizations — the glowing colors, the way sweat gleams on flesh — made me wonder if Tsukamoto would make all this look too much like fun, like a sport, for its own good. Again, nothing of the kind. One of the first times we actually see a boxer they're bruised like overripe fruit, and at one point Tsuda's face is so swollen from the beating he's taken it looks like it might burst. Boxing is bloodsport, emphasis on the blood, and Tsukamoto never lets us forget it, not least of all by giving both of these men dilemmas they can't punch their way out of.