How many movies have Izumi Sakai and Shunji Iwai collaborated on?

They have worked on 1 movie together! Their first movie together was ZARD yo Eien nare Sakai Izumi no Uta wa Kou Umareta (2019) and was their highest rated movie together. They have not worked together since ZARD yo Eien nare Sakai Izumi no Uta wa Kou Umareta (2019).