Background
Matou Kariya is the uncle of Matou Shinji, though he has actually severed ties with the Matou family for about ten years out of disgust. Disappointed with the lack of sorceric potential in Shinji and his father, Byakuya, Zōken blames Kariya for allowing the Matō's magical lineage decline since Kariya is the first in many generations to be naturally capable of sorcery.
While he loved his childhood friend Zenjou Aoi, he peacefully gives up trying to pursue her affections because she seemed to be happy accepting her engagement to Tohsaka Tokiomi. Aoi would later have two daughters, Rin and Sakura, who both came to like Kariya a great deal.