Civil servant Yor Briar has a secret identity: an assassin named the Thorn Princess. Lately, single women had been suspected of being spies, which was making Yor nervous. Meanwhile, Loid was searching for someone to play Anya's mother so they could attend the interview at Eden College. He just happens to run into Yor at a boutique. Anya reads Yor's mind and finds out that she's an assassin and tries to get Loid to ask Yor to play her mother.

Ostania's counterintelligence agency and national security bureau conducts spy hunts and keeps surveillance on its citizens to maintain peace within the country. They are also called the Secret Police and are feared. Yor's younger brother Yuri actually belongs to the Secret Police and is hunting down spies while keeping this a secret from Yor and others around him. One day, he suddenly shows up at the Forger residence. The Forgers, who are full of secrets, and Yuri, who has a secret identity, come face to face!