Kariya Matou is Shinji's uncle and the first member of his family to show real magical talent in generations—which made his decision to walk away from the Matou clan even more bitter. He'd cut ties with them over a decade before the 4th Holy Grail War, mostly because he couldn't stomach Zouken and the family's general direction. That left Zouken in a rough spot: he'd been counting on Kariya to carry on the magical bloodline, especially since Shinji turned out to be a dud in the talent department. A Master with actual powers was supposed to be essential for the Wars, so Zouken ended up resenting Kariya for letting things fall apart.
Still, Kariya never fully let go of his past. He stayed in touch with Aoi Zenjou, a childhood friend he'd been in love with, even after she married Tokiomi Tohsaka. That door had closed long before, and Kariya had accepted it. The couple's two daughters, Rin and Sakura, both ended up being fond of their uncle—one of the few genuine connections he maintained with anyone tied to the magical world.
Content compiled by AnimeList.moe from publicly available sources.
