I am dying to see a manga where Hashiras are teaming up (Well, there is the prequel manga, Stories of Fire and Water, but it's only Giyuu, Shinobu, Rengoku, and a Mizunoto-level Mitsuri), especially this duo. It has been said in the manga that these two respect each other's skills in battle, likely hinting that there is a possibility that they had worked together one time or another...