How many movies have Hachirō Kai and Yûsuke Koike collaborated on?

They have worked on 4 movies together! Their first movie together was Uno Kôichirô no uwaki nikki (1980) while their highest rated movie together was Female Teacher: Dirty Afternoon (1981). They have not worked together since Renzoku boko: Hakuchu no inmu (1982). They are most known for their drama films together.