The Hoodlum Soldier

First in a series of 9 films running 1965 to '72, all involving the unlikely pair of intellectual Arita and imperturbable, tough-as-a-post tho more cunning than smart ex-yakuza Kisaburo (is a wiki article on series, may be only the 1st & last freely available). This is standalone and surprisingly brutal - the amount of violence may be cartoonish but the individual bouts are not. Pretty grim going, pretty much well told (bar the overdone nature which would suit the release period IMO) and acted.