Diana, the second daughter of a frontier earl, has spent her life in a remote border region surrounded by her boisterous, muscle-brained brothers, living freely and without pretense. That carefree existence is upended when a royal decree forces her into an abrupt marriage. Her new husband is Lacilus, the son of a duke, renowned throughout the kingdom for his intelligence, good looks, and polished reputation as a perfect gentleman. The match is not born of romance: Lacilus had been betrothed to the kingdom's youngest princess, but she was sent to a neighboring country as part of a peace treaty, and a quick replacement marriage was arranged to avoid political complications. Diana, fully aware that she is a stand-in, cheerfully expects the worst. She openly jokes that a refined duke's son who lost a delicate princess would surely declare, "I have no intention of loving you!" Embracing her self-deprecating nickname of wild monkey, she enters the marriage with no expectations and no pretense of being a proper lady.

The story follows the resulting household as two opposites learn to coexist. Diana is straightforward, physically robust, and refreshingly unbothered by courtly manners, while Lacilus initially maintains a carefully crafted facade of gracious composure. Their dynamic revolves around mutual misunderstandings and slowly thawing distance: Diana's lack of romantic expectation leads her to treat the marriage as a practical arrangement, while Lacilus finds his polished exterior repeatedly challenged by her unfiltered honesty and capable, down-to-earth nature. Over time, their interactions move from awkward formality to genuine companionship, as each discovers unexpected depths in the other. Supporting characters include Diana's eccentric frontier family, whose blunt and physically imposing presence adds both comedy and warmth, and the broader noble circles that watch the unlikely couple with curiosity and occasional skepticism. The narrative arcs center on the gradual dissolution of Lacilus's mask, Diana's reluctant acceptance that she may be more valued than she assumed, and the pair's slow, heartwarming journey from a marriage of convenience to one of genuine mutual affection, all set against a light fantasy backdrop of a loosely constructed, fairy-tale-like kingdom.