Princess Diamond of the Jemnasty Kingdom has been feared and shunned her entire life because of her overwhelming beauty, a "gift" from the magic master Baroque Heat that made her an outcast among her own family. As a sacrificial offering, she is sent to live with a fearsome beast in the dreaded Forest of Despair. Contrary to expectations, the beast is the cursed form of Prince Gioald of the Tordria Kingdom, transformed by the magic of his cousin Libro and the mage Salita Tarotwork.

Diamond and the beast fall deeply in love. When she pledges her love with a kiss, the beast's magic breaks and the handsome Prince Gioald appears. However, Diamond is not pleased with this outcome, having genuinely preferred the beast's form. The two then set out on a journey to Tordria to find a way to reapply the magic and restore Gioald's beast appearance. The story follows this unconventional couple as they travel together, uncovering the political阴谋 that led to Gioald's original curse while dealing with Diamond's unusual preference for beasts over human beauty.

The narrative expands as Diamond and Gioald become entangled in world-shaking events. They later have triplet children named Onyx, Sapphire, and another sibling. The plot grows increasingly complex as the couple is eventually forced to become the world's "counterweights" or sacrifices for the planet's stability. Their children must navigate their parents' absence and the magical contracts that limit their ability to interact with them. The story incorporates elements of magic systems, royal politics across multiple kingdoms, and the mysterious powers of figures like Baroque Heat and the magical organization known as the Order of Magical Resonance in later arcs.