The Japanese title Shorinji Kenpo could be translated as "Shaolin Martial Arts", but that's not nearly violent-sounding enough for a Sonny Chiba film, so western audiences got KILLING MACHINE instead. It tells the story of Doshin So, founder of the real Shorinji Kenpo martial arts school/lineage, though it admits up front that it shouldn't be taken as accurate.
Doshin So travels in China and learns martial arts, then returns as an undercover agent for Japan during World War II. Taking Japan's loss of the war rather badly, he returns home and finds the country in ruins... bombed and burnt out, the economy in tatters and the yakuza running/ruining the place with prostitution, extortion and black marketeering.
Determined to help the poor and needy wherever he can, So fights off gangsters and GI's alike, runs up against the (corrupt) law and forms a dojo to teach his country men the edifying ways of the Shaolin Martial Arts… an all round good bloke for the most part, and only a KILLING MACHINE on his days off.
SHORINJI KENPO lacks the cheerfully exploitative sleaze of The Streetfighter, and suffers occasionally from a story that wants to have a nice message, but fumbles its way around it before blurting it out at the end like a shy teenager with a crush on you (as if you hadn't figured out what it wanted to say already). It wants to pay homage to the martial arts philosophy, and showcase some authentic techniques (though not, apparently, those of the real Shorinji Kenpo style), so it has to deliver some fight scenes. Chiba mostly beats up gangs of thugs, but in a more mannered and restrained way than in his pure exploitation films - except for a few moments when the film decides to throw in some gore and dismemberment to be on the safe side.
Without the bad-ass animalism of his character in THE STREETFIGHTER films, Chiba is certainly a less domineering presence on screen, but he carries off this part fairly well, though his performance couldn't be described as complex or nuanced. The cast around him range from very good to very bad, but mostly towards the good end. The direction of the film is mostly good, with some effective imagery and a good gritty feel for the post-war cities and towns. There is a bit of a tendency towards heavy handedness in places, and a bit of meandering in others, but mostly it gets the job done.
Overall, not a bad film, with some decent fights showing real martial arts - which means not nearly as flashy or cinematic as the Hong Kong kung fu films of the time. Definitely worth a look for Chiba fans, non-essential for everyone else.