This summary covers chapters 3 to 12 of the light novel, detailing the protagonist's journey and the unfolding political landscape.
The story centers on Serphil, a reincarnated individual from modern Japan who finds himself the third son of the Hyburg Duke family. In his new life, Serphil is initially disappointed by the medieval noble society and his father's neglect. However, he quickly adapts, using his modern knowledge to manipulate his way into favor with his siblings and the household staff. He orchestrates a plan that leads to his father's abdication and the smooth succession of his elder brother, Bart, as the new Duke. This involves subtly influencing the Duchess and the first concubine, fostering a sense of unity within the family, and ensuring the distribution of family assets. Serphil's efforts also secure a marriage alliance for his elder sister, stabilizing the Hyburg Duke family's position.
Seven years later, at thirteen, Serphil attends a graduation party at the Royal Academy. He witnesses a dramatic scene where Prince James Elserium, the Crown Prince, publicly breaks his engagement with Alicia Salem, the daughter of the Salem Duke family, accusing her of bullying the Saint Maril. Serphil, initially intending to remain a detached observer, intervenes when Alicia is falsely accused of pushing Saint Maril down the stairs. He uses his position as a representative of the Hyburg Duke family to question the Prince's accusations and expose the staged nature of the event. Serphil's sharp wit and understanding of political maneuvering quickly turn the tide. He points out that supporting the Prince would alienate the powerful Salem Duke family, causing a stir among the attendees.
Serphil orchestrates Alicia's escape and, through a clever negotiation, secures her agreement to accept the annulment while swearing her innocence to the King. He then confronts the false accusers, including the Garnet Viscountess, who is revealed to be a pawn of the Salem Duke family's rivals. Serphil forces the Garnet Viscountess to swear her own oath to the King, exposing her lie and dismantling the Prince's scheme. This intervention leads to significant political fallout: the Prime Minister, Knight Commander, and their sons are dismissed and exiled, while the Archbishop and merchant are demoted and their sons punished. The Garnet Viscountess's family is stripped of their title, and Saint Maril is confined to a church for life.
Following this incident, Serphil is summoned by his elder brother, Duke Bart. Bart reveals the consequences of Serphil's actions, including the political shifts and the fact that the King, influenced by the Salem Duke family's pressure and Serphil's intervention, has decreed that Serphil must marry by the time he graduates or be forced into a marriage with the Second Princess. This decree, coupled with the King's animosity towards Serphil for embarrassing the royal family, makes finding a suitable bride extremely difficult, as most high-ranking noble families are forbidden from engaging with him.
Serphil's situation becomes dire, as he is ostracized at school due to the King's decree and the fear of offending the royal family. During this time, he is approached by Grieda Arest, a young and powerful female Baroness. Grieda, impressed by Serphil's intelligence and the political maneuvering he displayed, proposes a marriage alliance. She reveals that her family, the Arest family, is a powerful military force that protects the kingdom's eastern border and is currently facing trade disputes with the King's favored concubine's family. Grieda sees an alliance with the Hyburg and Salem Dukes as a way to gain leverage against the King and improve her family's trade situation. Serphil, recognizing the mutual benefits and the protection Grieda offers, accepts her proposal.
The narrative then shifts to Serphil's daily life at school, where he is still ostracized but finds solace in his relationship with Grieda. Grieda, who is exceptionally strong and influential, often picks Serphil up from school on her horse, White King, much to the amusement and envy of their peers. Their relationship is characterized by Grieda's protective nature and Serphil's witty observations and modern knowledge, which he subtly uses to navigate the complex social and political landscape. Grieda, despite her imposing presence and military prowess, shows a softer side towards Serphil, often doting on him.
The story highlights the political machinations of the royal family, particularly the King and his favored concubine, Helena, who are portrayed as incompetent and self-serving. Serphil and Grieda, along with the Hyburg and Salem Dukes, form a powerful bloc that begins to counter the King's poor decisions. Serphil's past knowledge of history, particularly from Japanese culture, proves invaluable in understanding and predicting the political outcomes. He also uses his knowledge to introduce new culinary delights, like a simplified version of Neapolitan pasta, to the Hyburg Duke's household, improving their quality of life.
The chapters conclude with Serphil and Grieda attending a play that mirrors their own situation, with Grieda playing the role of a powerful warrior and Serphil a beautiful maiden. Their relationship deepens, and they continue to navigate the treacherous political waters, supported by their respective families and allies, while the King's incompetence continues to destabilize the kingdom.