The fragile peace between the neighboring nations of Ostania and Westalis is constantly threatened by corrupt politicians, radical nationalists, and other warmongering groups. Despite these dangers, the legendary spy and master of disguise known as "Twilight" carries out perilous missions one after another, driven by the hope that no child will ever have to endure the horrors of war.
In the busy Ostanian city of Berlint, Twilight adopts the alias "Loid Forger," posing as a respected psychiatrist. His real goal, however, is to gather intelligence on the influential politician Donovan Desmond, who rarely appears in public except at his sons' school—the prestigious Eden Academy. To accomplish this, Loid recruits unmarried city hall clerk Yor Briar to play the role of his wife and adopts the curious six-year-old orphan Anya as his daughter. His plan is to enroll Anya in Eden Academy, where he hopes she will excel, giving him a chance to meet Donovan without raising suspicion.
Unfortunately for Loid, even a man of his skills finds it difficult to convincingly act as a loving father and husband. And just as Loid hides his true identity, Yor—a secret assassin known as the "Thorn Princess"—and Anya—a telepath with the ability to read minds—have no intention of revealing their own secrets either. Though this seemingly perfect family is built on lies, the Forgers gradually realize that the love they have for one another surpasses all else.