I Suddenly Became the Second Female Lead in a Book

I never imagined that I would become a character in my own book. I never imagined that I would die, either. I decided the endings for every character, and even controlled every last thing. But when I became her, when I became part of the book, I realized for the first time that I had never truly lived all those years. For the first time, I was really alive. For the first time, I thought about what I wanted to do. For the first time, I made a decision for myself instead of for her. What will my ending be? I don't know. But one thing is certain: the world I live in now is no longer the world I created. And yet, it is still that same world, just different. Cause and effect, whatever the cause and whatever the effect, they are all there. Nothing will change, or perhaps everything will change.