Uryuu Ishida's father. He also knows the way of the Quincy and was one of the most powerful but he finds it a waste of time. He has mentioned that while his son has the heart of a Quincy he himself has the power when he is training his son to get back his Quincy powers. He promises to train him but he must give up his friendship with Ichigo. Although he refuses to take put in Quincy activities he shows his distaste for Shinigami. He also reveals that he knew Ichigo's father in the past and in the short clips at the end of the episodes it shows them together, usually ending with Ryuken using his Quincy powers to fire arrows at Isshin after he teases or tries to show pictures of their past. They are both doctors with Ryuken running a hospital and Isshin running a clinic.