In the kingdom of Welbeza, Alice Coleman is the long-suffering daughter of an impoverished noble family. For years she has been verbally and emotionally abused by her childhood friend Grey, the heir to a marquis household. When her parents announce that an engagement to Grey has been arranged, Alice is desperate to escape it. In a moment of panic, she blurts out that she already has a higher-ranking suitor. To make the lie real, she embarks on a reckless plan: she will propose marriage to the first man who passes through the school gate, hoping someone, anyone, will accept.

The first person she approaches is Arthur Grindelbard, the heir to the nation's most powerful ducal house and the object of every noble girl's admiration. To her shock, Arthur not only accepts her stammering proposal on the spot but does so with a radiant smile and a vow to do anything for her. What begins as a desperate gamble quickly becomes far more complicated. Arthur showers Alice with expensive gifts, insists on escorting her everywhere, moves her into his mansion, and even locks her room from the outside. His devotion is overwhelming and possessive, and Alice cannot understand why a man of his standing would lavish such attention on a timid, self-doubting commoner noble.

As Alice tries to navigate her new role as the future duchess, she faces obstacles from every side. Grey, who has always tormented her, refuses to let her go and reveals a hidden reason for his cruelty. Rival noblewomen, including Arthur's former fiancée Chloe, scheme to humiliate and harm her. Yet in every crisis, Arthur's love only intensifies. He becomes increasingly protective, even controlling, vowing that no one will ever touch her again.

Woven through the present-day romance is a hidden past. Strange dreams begin to visit Alice, memories of a sickly boy named Aslan whom she used to visit in the hospital as a child. Through conversations with Arthur's father and other clues, she gradually realizes that Aslan and Arthur are the same person. Years ago, when Arthur was gravely ill and isolated, young Alice was the only one who treated him with kindness and without fear. Her sudden disappearance from his life left a wound he has never forgotten. Now grown, Arthur has engineered their meeting and engagement, determined never to lose her again.

The story follows Alice's struggle to gain confidence as a future duchess, the unraveling of Grey's conflicted feelings, the threat posed by jealous rivals, and the slow revelation of the childhood bond that binds the central couple. Arthur's love is both a safe harbor and a gilded cage, and Alice must decide whether she can accept the full weight of his devotion.