Ryuken Ishida is Uryuu's father and a trained Quincy himself—one of the most powerful around, though he's made it clear he considers the whole thing kind of a waste of time. When he agrees to help his son recover his Quincy abilities, he makes it brutally clear: Uryuu will have to drop his friendship with Ichigo. Ryuken's got the raw power; his son's just got the heart for it.
Despite staying mostly out of Quincy business, Ryuken doesn't hide his disdain for Shinigami. That said, he's got actual history with Ichigo's father Isshin—they knew each other back in the day, something the omake shorts occasionally reference. Those clips usually show them messing around together, with Ryuken ending the fun by firing Quincy arrows at Isshin whenever he gets too cocky or tries pulling out old photos.
Both men ended up in the medical field: Ryuken runs a full hospital while Isshin operates a small clinic.
Content compiled by AnimeList.moe from publicly available sources.
