How many movies have Masaharu Koyama and Seiji Matsuda collaborated on?

They have worked on 6 movies together! Their first movie together was Gyo: Tokyo Fish Attack (2012) while their highest rated movie together was Demon Slayer -Kimetsu no Yaiba- The Movie: Mugen Train (2020). They have not worked together since Demon Slayer -Kimetsu no Yaiba- The Movie: Mugen Train (2020). They are most known for their animation films together.