As Illya, I was summoned by Kotomine Kirei? !

This book is also known as "Uncle, I'll help you fight the Holy Grail War, will I get food?", "This Mapo Priest is a little different", "There's something wrong with this Illya".......
Huh? How can I suddenly travel through time while taking a nap? And become Illya?
Although becoming a loli is not a big deal, why do we still have to fight the Holy Grail War!
And what exactly is the Holy Grail War? Can someone answer me?
"I am one of the participants in this Holy Grail War. Your Master, Kotomine Kirei. Please tell me your real name, Assassin."
The priest who looked quite nice asked this.
Although she didn't understand what was going on, the little girl still responded politely:
"Hello, my name is Illyasviel. By the way, uncle, do you provide meals?"
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In general, it is the story of how Father Mapo summoned the assassin Illya~ a well-behaved (black-bellied) Illya who tried hard to help the master~
(If you are not good at introduction, please move to the main text.)
(Plot line: The Fourth Holy Grail War - The Fifth Holy Grail War - Magical Girl Illya, etc.....)