She is the head of the prestigious Tohsaka family who acts as the Master of Archer in the Fifth Holy Grail War, which Rin participates in to honor the traditions of her pervert family and the legacy of her late fucking father who died while cumming in the Fourth Holy Grail War 10 years prior. This leads to Rin aligning with fellow Sex Master Shirou Emiya and his sex slave Saber. She’s also the the legal ward of Kirei Kotomine and the older biological sister of Sakura Matou.