How many movies have Kôji Yamazaki and Yasunari Kubota collaborated on?

They have worked on 4 movies together! Their first movie together was Sister Incest: Naughty Magical Breasts (2013) while their highest rated movie together was Milk the Maid (2013). They have not worked together since Nôsatsu sales: Iyashino ero-shitagi (2015).