This is kinda worthless. Don't get me wrong, I like the original manga but this prequel ruins it for me, I prefer to think of it as if this prequel doesn't exists.
I know that at the end of the day, everything we are reading is fiction, but that does not means I want the story within the story to be also fictional, is kinda cruel and sad, after all if the characters are not even real within their own story, then all the hardships, all the accomplishments they made, all the suffering, was pointless, it was just an illusion made by the girl.
It might have been different if she made the illusion into reality, but if it is just an illusion...... is like the Matrix, but there is not "outside" world or a way to be free of it, because the characters are not even real to begin with.