How many movies have Kouichirou Natsume and Yukiko Aikei collaborated on?

They have worked on 4 movies together! Their first movie together was Naruto Shippuden the Movie: The Will of Fire (2009) while their highest rated movie together was The Anthem of the Heart (2015). They have not worked together since The Anthem of the Heart (2015). They are most known for their animation films together.