How many movies have Jirō Ishikawa and Ryō Kaihara collaborated on?

They have worked on 15 movies together! Their first movie together was 華と蛇　～狂気の旋律～ (2005) while their highest rated movie together was New Hotaru The Hyper Swindler 4 (2006). They have not worked together since Scissor Penis (2018).