Well if you've seen and loved Kinji Fukasaku's other great yakuza flicks, there's no harm in checking out Doberman Cop, but be warned it's nowhere near as good as, say, The Yakuza Papers or Graveyard of Honour.
It was probably shot very hastily with low production values, and it shows. The camera work is remarkably so so for a Fukasaku movie and here his trademark kinetic style could be mistaken for shoddy hand-held camera work. Everything from the sets to the fights just shows there wasn't much creativity involved. It's a pretty standard yakuza effort, probably shot together in 2 weeks to meet Japan's demands for the product.
Sonny Chiba stars as the naive village cop that comes to the big city of Tokyo to track down a missing girl from his village. There's a fair amount of anti-establishment bikers, crazy cops, yakuzas, prostitutes, star-system sleazebags, but what makes Doberman Cop worthwhile is Sonny Chiba. The guy is a badass, there's no way around that. And he gets to show his asskicking skills on a number of occasions, thank god. He also carries a pig. Good, not great stuff but worth a watch.