Adopted daughter of the Archduke and an Archduke Candidate. She has memories of living in Japan as Urano Motosu until adulthood. She was reincarnated into another world after being buried by books. She loves books above all else and struggled to make them since she was a commoner. She often takes eccentric actions, such as becoming a shrine maiden apprentice after discovering the temple library. She calls her parents "Adoptive Father" and "Adoptive Mother." After being attacked by Count Bindewald, she became the Archduke's adopted daughter to protect her family. *At that time, her name was changed from Myne to Rozemyne.

Male member of the Archducal family. Rozemyne's guardian, he has looked after her since her time as Myne. He loves experiments and is described by Rozemyne as a mad scientist. He rarely shows emotion on his face, but those close to him can tell. In social settings, he wears a sparkling smile (though he is extremely grumpy underneath). When he enters a hidden room with Rozemyne, it is usually time for a lecture.

The Aub (Archduke) of Ehrenfest. Male. The person who adopted Rozemyne. He dislikes social duties and honestly wants to run away from them. When no one but the Archducal family is in the room, he takes off his mask as a lord and slacks off. Ferdinand's younger half-brother. He is loathed by Georgine.

Archduke Candidate of the Archducal family. Rozemyne's older brother (by adoption). He calls her "Rozemyne." A mischievous boy whose personality is just like his father's. He is fundamentally honest and sincere. He is poor at deception, schemes, and reading between the lines. He is a boy of his age who cares about looking cool and wants to show his best side to his younger siblings. While being dragged along by and trying to restrain Rozemyne's rampages, he maintains grades on par with candidates from greater duchies.

A lovely, refined, and graceful girl, though she lacks the dignity expected of a princess from the second-ranked duchy. She has a complex about her own bad timing and earnestly prays to Dregarnuhr, the Goddess of Time, to improve it. Because she bluffed that she "didn't dislike reading" at a first-year tea party, Rozemyne labeled her a "book-loving friend" and invited her to join the library committee. She used to find difficult books intimidating, but her eyes were opened to the joy of reading after encountering the romance stories published by Ehrenfest. She has become close enough with Rozemyne to hold an annual "Bookworm Tea Party" along with the librarian Solange to exchange books. Rozemyne describes her as a "soul mate," and Hannelore considers her a precious friend who shows her genuine, straightforward affection.