You'll have to see the real ending to get this trophy. To do so you need to reveal all Truths. There are four Truths and in order to reveal them you'll need to gain information about Lapino, Zenobia, Iblis Stone, and Skyripper.
As soon as you have revealed all four Truths the book's pages will flip and the choice with a golden key will appear. Choose it to begin the true story. Immediately you'll be presented with two more choices and again pick the one with the golden key.