The story begins with Luxida Fientzen, the fourth daughter of a financially struggling Count, being informed by her father of an arranged marriage to Eluid, the heir of the prestigious Duke Zeekseln. Luxida, who has largely avoided noble society due to her family's financial constraints and her own preference for a quiet life of gardening and reading, is surprised but resigned, as marriage is expected for women her age. She learns that Eluid is widely known as the "Chubby Duke" due to his rumored clumsiness, shyness, reclusiveness, and peculiar habit of playing with dolls. Despite these negative rumors, which have caused numerous noble ladies to reject him, the Duke's family is desperate for the marriage, showering Luxida's family with extravagant gifts that far exceed the dowry they would normally have to provide.
Luxida visits the Duke's mansion, which is more akin to a castle, and meets Duke Gauzein Zeekseln, a formidable former general. He is overjoyed at the prospect of the marriage, having already informed the King and begun wedding preparations. Luxida, however, insists on meeting Eluid before the wedding. The Duke reluctantly agrees, revealing Eluid's introverted nature and tendency to become engrossed in his hobbies. Luxida is led to Eluid's room, a vast space filled with meticulously crafted wooden dolls depicting soldiers and battle scenes. Eluid, a slightly plump young man with blond hair and green eyes, is engrossed in a war game simulation with his dolls. Luxida, recognizing the scenario as the Battle of Cannae, inadvertently reveals her knowledge, impressing Eluid. After a playful challenge where Luxida manipulates the game, Eluid finally notices her. Despite his initial shock and embarrassment, Luxida declares her intention to marry him, having found him intriguing.
Following their engagement, Luxida faces the challenge of preparing for a wedding of royal scale, as she lacks the refined etiquette expected of a future Duchess. She diligently undergoes training, while also overseeing the preparation of her new rooms. Eluid, though agreeing to the marriage due to his father's strong persuasion, remains extremely shy and avoids Luxida, often becoming flustered in her presence. Luxida attempts to communicate with him through their attendants, and Eluid eventually grants her freedom in decorating their shared spaces, expressing concern about whether she truly wishes to marry him. Luxida, determined to build a relationship, adopts a patient approach, comparing it to nursing an injured bird. Over time, Eluid gradually becomes more comfortable with her, and they begin to exchange simple conversations.
Their wedding is a grand affair attended by royalty and high nobility. During the ceremony, Eluid, overwhelmed by the crowd, freezes. Luxida, using military commands, helps him through the ritual, demonstrating her understanding of his personality. After the wedding, Luxida's social standing elevates, and she actively participates in royal events. She learns that Eluid's initial reclusiveness stemmed from past negative experiences with potential brides and his father's high expectations. The Crown Prince, a close friend of Eluid's from childhood, initially viewed Luxida with suspicion but warms to her as he sees her genuine affection for Eluid and her efforts to support him.
A significant turning point occurs when a noblewoman, who had previously rejected Eluid, insults him at a ball. Luxida, fiercely protective of her husband, publicly rebukes the noblewoman, leading to her disgrace and the strengthening of Luxida's reputation as a loyal wife. Eluid, inspired by Luxida's support, gradually becomes more confident. Their relationship deepens through their shared interest in military strategy games, which Eluid uses to teach Luxida. He begins to open up to her, sharing his passion for military history and strategy.
The kingdom faces a looming war with the neighboring Aibaru nation, which has allied with the Halbart Kingdom. Eluid, despite his introverted nature, is recognized for his strategic brilliance and is ordered by the Crown Prince to join the war effort as a chief strategist. Luxida, initially concerned about Eluid's ability to cope with the battlefield, decides to accompany him, much to his surprise and initial protest. She believes her presence will provide him with the support he needs. Eluid, deeply moved by her devotion and determination, accepts her presence, vowing to protect her and the kingdom. He promises to become a true husband to her after the war.
Eluid departs for the front lines, leaving Luxida to manage the kingdom's logistical support for the war effort. She organizes the collection and delivery of supplies and hosts elaborate social events to maintain morale and project an image of strength. After months of intense fighting, the kingdom achieves a decisive victory. Eluid, hailed as a hero, returns to the capital, having undergone a significant transformation. He is now physically leaner and more confident, though still deeply devoted to Luxida. Their reunion is marked by a passionate embrace and a renewed commitment to their marriage, with Eluid finally ready to consummate their union. The story concludes with the implication of their continued happiness and Eluid's growing role in the kingdom's military and political affairs.
