How many movies have Kappei Yamaguchi and Shigenobu Nagasaki collaborated on?

They have worked on 4 movies together! Their first movie together was Rurouni Kenshin: Requiem for the Ishin Patriots (1997) while their highest rated movie together was One Piece Film: Strong World (2009). They have not worked together since One Piece Film: Strong World (2009). They are most known for their animation films together.