Corrupt politicians, frenzied nationalists, and other warmongering forces constantly jeopardize the thin veneer of peace between neighboring countries Ostania and Westalis. In spite of their plots, renowned spy and master of disguise "Twilight" fulfills dangerous missions one after another in the hope that no child will have to experience the horrors of war. In the bustling Ostanian city of Berlint, Twilight dons the alias of "Loid Forger," an esteemed psychiatrist. However, his true intention is to gather intelligence on prominent politician Donovan Desmond, who only appears rarely in public at his sons' school: the prestigious Eden Academy. Enlisting the help of unmarried city hall clerk Yor Briar to act as his wife and adopting the curious six-year-old orphan Anya as his daughter, Loid enacts his master plan. He will enroll Anya in Eden Academy, where Loid hopes she will excel and give him the opportunity to meet Donovan without arousing suspicion. Unfortunately for Loid, even a man of his talents has trouble playing the figure of a loving father and husband. And just like Loid is hiding his true identity, Yor—who is an underground assassin known as "Thorn Princess"—and Anya—an esper who can read people's minds—have no plans to disclose their own secrets either. Although this picture-perfect family is founded on deception, the Forgers gradually come to understand that the love they share for one another trumps all else. [Written by MAL Rewrite]

In Japan, there exists a government agency known as the Supernatural Disaster Countermeasures Division (SDCD), whose duty is to protect the citizens from creatures unseen. They are able to dispatch these monsters swiftly and without alerting the general public. But currently, they face a different challenge: the betrayal of one of their own. After the death of her mother several years ago, Kagura Tsuchimiya has been fostered by the Isayama family and forms a close sister-like bond with their daughter Yomi. The two become inseparable, and together they work for the SDCD as highly skilled exorcists. However, as the stress and consequences of their sacred duty weigh on them both, and family politics come into play, Kagura and Yomi begin to slowly drift apart. One of them grows earnestly into her role as an exorcist, and the other heads down a dark path from which there may be no redemption... [Written by MAL Rewrite]