How many movies have Akio Watanabe and Akiyuki Shinbo collaborated on?

They have worked on 4 movies together! Their first movie together was Kizumonogatari Part 1: Tekketsu (2016) while their highest rated movie together was Kizumonogatari Part 2: Nekketsu (2016). They have not worked together since Fireworks (2017). They are most known for their fantasy films together.