How many movies have Akira Kasahara and Shuichi Okubo collaborated on?

They have worked on 4 movies together! Their first movie together was Go! Anpanman: Baikinman's Counterattack (1990) while their highest rated movie together was Go! Anpanman: Tears of the Mermaid Princess (2000). They have not worked together since Go! Anpanman: Gomira's Star (2001). They are most known for their animation films together.