Synopsis for
Shinjuku Mad (1970) More at IMDbPro »Shinjuku maddo (original title)

A man comes to Tokyo from the countryside looking for his son's killer. He discovers the slow pace of police investigations and willing to understand the reasons of his son's death slowly enters in the deep underground of the city and encounters its counterculture symbols. Finally he finds Shinjuku Mad the man that he's been told has killed his son. He's the leader of a self-called rivolutionary gang and explains to the man that his son was a rat and they had to remove all the possible obstacles on the road to revolution. But in the final verbal showdown the gang's reasons appear as inconsistent, their will to make a revolution is weak and they don't even know what to revolt.