She is an English teacher at Shirou's school, homeroom instructor of Shirou's class and the supervising teacher for the archery dojo. She is widely called "Tiger," a nickname she dislikes ("Taiga" and "Tiger" sound similar in Japanese), though Shirou refers to her as "Fuji-nee" (older sister Fuji). After Kiritsugu died, Taiga became Shirou's guardian and has been living with him for several years. Taiga and Shirou are very close, and she regards him as a younger brother.
She's initially distrustful of Saber, believing that "some strange woman was trying to take Shirou from her" as she put it. She becomes exasperated whenever a new girl appears at Shirou's house, thinking he stashes girls at his house. Taiga always shows up for breakfast and dinner at Shirou's house to have some of Sakura's cooking, and always saves some scraps from breakfast for her lunch.
During Rider's Blood Fort attack on Shirou's school, Taiga was the only person who could still move around somewhat. Begging Shinji Matou for help, he quickly kicks her in the head, knocking her unconscious. She recovers quickly though, even pigging-out on hospital food while recovering.