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.

Eden's legendary dessert finally appears! In order to obtain the macaroons that supposedly can make you into an Imperial Scholar if eaten, Anya and her friends race to get to them first.

On a mission as Thorn Princess and using her job as city hall as a cover, Yor is tasked with protecting the only survivors of the Gretcher family, Olka and her son, and helping them escape to a different country by traveling on a cruise ship.