A young woman named Maomao, an apothecary raised in the pleasure district of a city inspired by ancient China, is kidnapped and sold into servitude in the inner palace of the Emperor. The rear palace is a sprawling complex where the Emperor's consorts and their ladies-in-waiting reside, a world of rigid social hierarchy, political maneuvering, and hidden dangers. Determined to live an inconspicuous life as a simple servant, Maomao's plans change when she learns that the Emperor's infant heirs have fallen mysteriously ill. Using her extensive knowledge of medicine and poisons, she secretly intervenes, identifying that toxic face powder is the cause. Her actions catch the attention of Jinshi, a beautiful and enigmatic high-ranking eunuch who manages the palace. Intrigued by her intellect and indifference to his charm, he promotes her to lady-in-waiting and food taster for the Emperor's favored consort, Lady Gyokuyo. Maomao finds herself reluctantly drawn into a web of courtly mysteries, from apparent curses and poisonings to suspicious deaths and political conspiracies, solving each case with her scientific mind and sharp observational skills while navigating her growing, complicated relationship with the persistent Jinshi.

The upcoming animated feature film, scheduled for release in December 2026, will present an entirely new, original story crafted by the series' author, Natsu Hyuga. While specific plot details remain under wraps, the film is expected to continue following the protagonist Maomao as she applies her apothecary expertise to unravel a fresh mystery within or potentially beyond the walls of the imperial court. The movie will feature the return of the main characters, including the sharp-witted Maomao, the powerful official Jinshi who takes a special interest in her, and Consort Gyokuyo, who provides Maomao with her position and protection. The narrative is anticipated to expand upon the established world of the series, exploring new forms of intrigue and danger while maintaining the core elements of deductive reasoning, historical atmosphere, and the complex social dynamics that define the story. The film is being produced as a companion piece to the upcoming third season of the anime, offering fans a significant new chapter in the acclaimed franchise.