What would happen if Chelsea wasn't killed? What would happen if an unknown swordsman suddenly jumped in the battle? Would the Night Raid's destiny be rewritten? Fate is a book...only to be written by the author himself, not anyone else. That one person will change the fate of that world.

There is a saying that when you die, your entire life flashes before your eyes like a movie. Robin saves the world from great calamity, at a great cost. As he accomplishes his final deed, he reminisces about his past as if reading a book, the book of infinite possibilities, called the book of Fate. The story will continue as Robin returns fulfilling his promise to Lucina.