The heroine of this work. Even in the original story she’s a main heroine. Prisma☆Illya was Illya’s route to capture Miyu! (half-serious)
The initial concept is “a reverse Illya at a different world.” While the Illya from the original work Fate is a completely different being, they are girls with many points in common.
A child with the power to grant wishes, inserted in a great destiny, from a family not connected by blood, and who absolutely had to protect the protagonist.
Due to Shirou’s strenuous effort, she somehow reached a normal ending, but taking this from the true to the good ending is Illya’s role. The popularity is already at MAX, so all that has to be done is to advance in the story!