How many movies have Koudai Watanabe and Mayumi Tanaka collaborated on?

They have worked on 2 movies together! Their first movie together was One Piece "3D2Y": Overcome Ace's Death! Luffy's Vow to his Friends (2014) while their highest rated movie together was One Piece Film: GOLD (2016). They have not worked together since One Piece Film: GOLD (2016).