Miyu Edelfelt is a young girl who serves under Luvia as a magical girl. Her origin is unknown, except that she has a brother who looks similar to Shirou, and she takes on the Edelfelt name after being taken in by Luvia. She lives in Luvia's mansion and acts as her maid to earn her keep. She uses Ruby's sister Kaleidostick, Sapphire, in order to transform, and she initially has a much better understanding of her abilities than Illya. She takes her role very seriously and treats Illya as a bothersome rival, though they eventually become close friends.

(Source: Type-Moon Wiki)