Shirō's adoptive older sister. Illya is portrayed within the series as a spoiled brat, throwing tantrums when she doesn't get her way. She is in love with Shirō (who only loves her as a sibling) and is very possessive of him. She sees the other girls as threats and constantly battles with Rin for Shirō's attention. She is not above using her magecraft to get her way, including the use of a sleep spell on Shirō, followed by a paralyzing curse so that she would either have the opportunity to sleep next to him or "awaken" him with a kiss. She is one of the announcers of the Holy Grail War in the first episode, though her servant Berserker still competes by himself.