Ishida Ryuuken is a Quincy and the father of everyone's favorite dork, Uryuu. Far from being anyone's favorite anybody, Ryuuken is cold, indifferent, harsh, critical, condescending, and pitiless – none of the words that best describe him are particularly flattering. When he was first introduced in Uryuu's flashbacks, Ryuuken expressed complete indifference to Quincy, Shinigami, and Hollows alike. "I have no interest in it," he tells a young and unhappy Uryuu, "And you [Uryuu] have no talent in it". When Uryuu asks why he hates being a Quincy so much, Ryuuken simply says, "Because you can't make a living from it". Ryuuken is of the opinion that Hollows are the Shinigami's problem; its better to fight for those who are still alive than worry about those who are dead.

Having expressed no interest in being a Quincy, Uryuu assumed that Ryuuken got rid of his Quincy powers long ago. Quiet the opposite is true, as Uryuu discovers: Ryuuken is in fact a very powerful Quincy, one who possesses the Quincy Cross and has mastered every technique developed by Souken. Somehow, he was fully aware that Uryuu went to the Soul Society and lost his powers there. To top it off, Ryuuken has the ability to perform the impossible: to give Uryuu his lost powers back.

Ryuuken and Uryuu have an estranged relationship. Ryuuken calls Uryuu pathetic and cowardly, and was critical and unsupportive of his Quincy training when Uryuu was growing up. He doesn't seem particularly concerned with Uryuu's safety, even at one point threating to kill him (Chapter 214). For his part, Uryuu doesn't entirely trust Ryuuken and calls him by his name, rather than respectfully calling him "Father". However, in an early flashback Uryuu remembers discussing Ryuuken's condemnation of the Quincy with Souken, his master. What Souken understands, and what Uryuu has yet to realize, is that Ryuuken's sense of justice stems from his desire to protect the things that are dear to him (Chapter 124). The implication is that Ryuuken is concerned about his family (read: Uryuu). However, as Ryuuken explains to Kurosaki Isshin in Chapter 241, the choice of whether or not his son lives or dies is entirely up to Uryuu himself.