How many movies have Kappei Yamaguchi and Yuuji Ikeda collaborated on?

They have worked on 4 movies together! Their first movie together was Boyfriend (1992) while their highest rated movie together was One Piece: Dead End Adventure (2003). They have not worked together since One Piece: Episode of Chopper Plus: Bloom in the Winter, Miracle Cherry Blossom (2008). They are most known for their animation films together.