"Salaryman" is a Japanese term for somebody who works for a company in a boring job, not really going anywhere, working just to survive. They're generally charicatured as meek individuals without much of a personality, and looked down upon (even by other Salarymen, probably). Salaryman Kintaro is different! The former leader of a biker gang he's tough, honourable, brave and rather good looking. He's a very popular character in Japan, with his own manga, anime, tv-series and a few movies - the first of which was the Miike directed effort under discussion.
At or near the start of the film, Kintaro is transferred to a branch of the construction company where he works that's run by a curmudgeonly drunk. He attends various meetings where rival firms bid for public contracts, but they don't win any. When they are just narrowly underbid on a contract that Kintaro is *sure* they had gotten to the lowest possible price, he realises that something underhand is going on, and that officials are being bribed by a competitor. This is something he's not going to stand for!
Now that might sound really dull, but it's not. Slightly dull, yes, but the characters are all likeable/interesting enough to make us care about their business affairs - and we get more focus on their personal lives anyway. The film makes only minimal effort to provide the backstory for the characters, who are presumably familiar to the Japanese audience that would go to see the film already. The relationships between some of the characters is still unclear to me, in fact, as if I'd started watching a TV series on the second episode. This may explain why the film isn't highly regarded by Miike fans, who don't know the characters and aren't as moved by what happens to them in the film as a Kintaro fan might be.
The other reason it's probably not held in high regard is probably because it's a very "tame" film by Miike standards. Well, by the standards of the most famous Miike films anyway - he has made quite a few films without blood, guts and sex in them, but they're not the ones that have received wide distribution. Kintaro is free of guts and sex, and the blood that's shed is on quite mild, human standards (no gushing arteries here). It's a Miike film that you could watch with your young relatives, and they might even enjoy it. It's never going to achieve the kind of cult fanbase that films like Ichi The Killer do, because it's not unique or different enough, and doesn't have anything that's going to raise any extreme emotions in the viewer unless they're rabid Kintaro fans... but it's an engaging story of some likeable characters, and competently directed.