How many movies have Hachirō Kai and Yoshihiro Kawasaki collaborated on?

They have worked on 6 movies together! Their first movie together was Sekkusu dokku: Midarana chiryō (1980) while their highest rated movie together was Uno Koichiro no Hiraite Utsushite (1981). They have not worked together since Young Girls' Holding Cell (1982).