The protagonist, a young woman who mysteriously transmigrated from modern Japan, finds herself in a medieval European-esque world. After a year of acclimatization, she is presented as a "rare beast" and a "princess from a neighboring country" to the King as tribute. She is housed in the King's harem, a place called the "inner palace," where she lives a relatively comfortable life, learning the language with the help of her attendant, Cyril, and enjoying the food.
Her peaceful existence is disrupted when the King, a stern and imposing figure, encounters her in the library. He questions her abilities and learns she is still learning the language. Later that evening, he visits her room and bestows upon her the name "Nafafistea." When she struggles with the pronunciation and requests the spelling, she inadvertently draws a map of the inner palace, which the King confiscates and destroys, warning her against suspicious actions. He then assigns her a teacher, Segju, a former high-ranking priest, to improve her education and language skills.
Under Segju's tutelage, Nafafistea learns history, culture, and mathematics, discovering that her new world is not Earth and that the general populace is unaware of its spherical nature. She also learns that her current status is that of a "concubine candidate," not a full concubine, and that becoming a concubine depends on the King's summons. She expresses a desire not to become a concubine, citing the King's age and her own perceived lack of beauty.
The King, initially believing Nafafistea to be a child, begins visiting her room. These visits are physically painful for her due to the size difference between them, and she repeatedly expresses her discomfort. The King, however, dismisses her pain and insists she will get used to it. This leads to a series of unpleasant encounters, during which Nafafistea attempts to resist and express her pain, often met with the King's cold indifference or threats.
Following a particularly distressing incident, Nafafistea feigns illness, claiming stress-induced gastritis and requesting that the King refrain from visiting for a few days. This, coupled with the arrival of three puppies she acquired for "poison testing," leads to a temporary reprieve from the King's visits. However, she also begins to face harassment from other concubines, who mock her and leave dead animals and foul-smelling gifts outside her cottage.
After a period of relative peace, the King resumes his visits. Nafafistea, realizing the King is accustomed to flattery and subservience, decides to feign a more compliant and appreciative demeanor to distance herself from him. She expresses gratitude for gifts and compliments his appearance, while subtly hinting at her desire for freedom. This strategy initially pleases the King, but his interest wanes as her act becomes routine.
Meanwhile, political tensions rise in the palace as the King approaches an age where an heir is expected. A poisoning incident involving several concubines, with Nafafistea falsely implicated, leads to an investigation. Nafafistea, using information gathered through her observations, helps expose the culprits. As a reward for her assistance and to quell the unrest, she is granted permission to visit the city with an escort.
During her outing, Nafafistea sells the gifts she received from the King to fund her activities, enjoying a rare taste of freedom. The King, observing her through reports, begins to realize his misjudgment of her. He learns she is not a child but a grown woman who deliberately misled him to avoid his advances. He also discovers her genuine desire for freedom and her simple pleasures, like spending time with her dogs and enjoying sweets.
The King, now aware of his past transgressions and Nafafistea's true nature, feels a sense of regret and a growing desire to reconnect with her. He invites her to a ball, intending to apologize and perhaps rekindle a genuine connection, but she remains wary and distant. The narrative concludes with Nafafistea, now a young woman, enjoying a peaceful life with her dogs, while the King grapples with his past actions and the possibility of a genuine relationship with her.
