How many movies have Ken Arto and Sumiko Aihara collaborated on?

They have worked on 2 movies together! Their first movie together was City Hunter: Shinjuku Private Eyes (2019) 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).