The delicate peace between Ostania and Westalis remains perpetually endangered by corrupt officials, extremist nationalist groups, and various aggressive factions. In response to these threats, the legendary spy and master of disguise known as "Twilight" undertakes dangerous missions without rest, fueled by a desire to shield future generations from the horrors of war. Within the Ostanian city of Berlint, Twilight assumes the alias "Loid Forger," posing as a respected psychiatrist. His true goal is to gather intelligence on the prominent politician Donovan Desmond, who seldom appears in public except at his children's school, the prestigious Eden Academy. To accomplish this, Loid recruits city hall employee Yor Briar to serve as his wife and adopts the mysterious six-year-old orphan Anya as his daughter. By securing Anya's enrollment at Eden Academy, Loid hopes to generate opportunities for discreet interactions with Donovan. Despite his expertise, Loid discovers that maintaining the facade of a devoted family is no simple feat. The situation becomes even more complicated by Yor, who is secretly an assassin known as the "Thorn Princess," and Anya, who possesses telepathic abilities; both conceal their true identities. Although this seemingly ideal family is constructed on lies, the Forgers gradually come to realize that the genuine affection they share transcends their deceptions.