How many movies have Kinichi Okubo and Maaya Sakamoto collaborated on?

They have worked on 4 movies together! Their first movie together was The Garden of Sinners: Paradox Spiral (2008) while their highest rated movie together was Is It Wrong to Try to Pick Up Girls in a Dungeon?: Arrow of the Orion (2019). They have not worked together since Is It Wrong to Try to Pick Up Girls in a Dungeon?: Arrow of the Orion (2019). They are most known for their animation films together.