How many movies have Yasutoshi Niwa and Yuichi Terao collaborated on?

They have worked on 6 movies together! Their first movie together was The Garden of Sinners: The Hollow Shrine (2008) while their highest rated movie together was The Garden of Sinners: Paradox Spiral (2008). They have not worked together since The Garden of Sinners: Future Gospel (2013). They are most known for their animation films together.