A former member of The Order, now working against the JAA after being banished by them. He was a senpai to Shishiba. Yotsumura is one of the strongest known assassins, shown being able to hold his own solo against three active Order members (Shishiba, Nagumo, and Osaragi). He wields a three-section staff with a small, thin blade on one end. It is phenomenally sharp, being able to cut through an entire human body.

He is Amane's father. Amane's grudge against the JAA is because Yotsumura killed Amane's mother in front of him.