Berna, a young woman from a poor baronial family, works as a low-ranking maid in the royal castle to earn money to send back home. She is plain-looking, cheerful, and hardworking. Among her occasional duties is delivering laundry to the stables, where she sometimes crosses paths with Dietrich, the prince's personal guard knight. Dietrich is famed across the kingdom for his otherworldly beauty, with platinum-blond hair and emerald-green eyes, and his reserved, unreadable demeanor only adds to his mystique. Berna and Dietrich have built a small, easy rapport over brief exchanges in the stable yard, though Berna views him more as a pleasant spectacle than a romantic interest.

By royal command, Dietrich is ordered to marry Princess Cyana of the neighboring kingdom, a woman rumored to possess dangerous magical abilities and a cruel personality. Berna is assigned as waitstaff for the engagement party. When the princess arrives, she immediately casts a spell on Dietrich, publicly commanding him to propose to the one he truly loves. To the shock of everyone present—and to Berna's utter bewilderment—Dietrich walks past the princess and proposes to Berna instead. Enraged and humiliated, the princess retaliates by cursing Berna, shrinking her body into that of a small child.

The story traces Berna's disorienting new life as a child in a castle that no longer knows how to treat her, and Dietrich's steadfast claim over her as his betrothed. The princess is taken into custody, but the curse does not lift. Berna struggles with her new physique, her embarrassment at being carried around by the handsome knight she once barely dared to speak to, and the abrupt upheaval of her family's circumstances. Dietrich, in turn, sheds his usual emotional distance, showing a protective, patient, and increasingly tender side as he navigates legal hurdles, court gossip, and the mystery of the curse itself. Meanwhile, lingering questions thread through the narrative: whether the curse can be broken, what role Berna's often-mentioned older sister might play, and whether a genuine romance can take root between a young woman trapped in a child's body and the beautiful knight who chose her against all expectation.