A love triangle develops between a benevolent student, his innocent girlfriend, and a cruel petty criminal, all as a point of diagnosis of a social disease that had Japan slowly succumbing to lawlessness during the post-War era.

Perhaps Kobayashi's most sordid film, Black River is an exposé of the rampant corruption on and around U.S. military bases following World War II. Kobayashi spirals out from the story of a love triangle that develops between a good-natured student, his innocent girlfriend, and a coldhearted petty criminal (Tatsuya Nakadai, in his first major role) to diagnose a social disease that had Japan slowly succumbing to lawlessness, devolving into gangsterism, violence, and prostitution.—Anonymous