Hailing from a ducal family, Sylph Biebel has a duty to marry Prince Mikhail Luxborn and someday rule the nation. But Sylph dreams of becoming a librarian, an impossible goal for a lady. Yearning for the freedom her beloved books provide, she often sneaks into the royal library, posing as a commoner.

There, Sylph befriends Kanna Copierne, a fellow bookworm and secretly a noble. When their true identities are revealed, their friendship continues—until Sylph introduces Kanna to Mikhail. Kanna suddenly denounces Sylph as a jealous bully plotting to kill her. For that reason, Sylph is locked in a small cage and abandoned near the neighboring Kingdom of Dagenhelm to be devoured by its king, a man-eating monster.

However, Sylph is saved by Faber, the real king of Dagenhelm and actually a young man with a keen interest in stories. As Faber takes a liking to Sylph, even this girl who was unfairly pushed into the role of a villainess may seize her happily ever after.