Illya is easy to talk to and tends to be naive and carefree, she has had a normal childhood, growing up with no knowledge of magic or the Holy Grail War. She lives with her adored brother Shirou and is looked after by her maids Leysritt and Sella when her parents Kiritsugu and Irisviel are away. She is an ardent fan of anime. She secretly harbors feelings for her brother, Shirou. She was tricked by a magic wand named "Magical Ruby" into signing a contract and becoming a magical girl.