How many movies have Koichi Yamadera and Yō Yoshimura acted in together?

They have worked on 1 movie together! Their first movie together was Ranma ½: The Movie — The Battle of Nekonron: The Fight to Break the Rules! (1991) and was their highest rated movie together. They have not worked together since Ranma ½: The Movie — The Battle of Nekonron: The Fight to Break the Rules! (1991).