Therese Lithardt, a seventeen-year-old marquis's daughter, lives in an impoverished noble house, performing manual labor like sewing and gardening to support her family and fund her younger brother Elios's education. Her life takes an unexpected turn when she is summoned to the Grand Ducal castle of Accloud. The young Grand Duke Leon Accloud, a capable but publicly reclusive nineteen-year-old, is seeking a bride through the ancient "Ring Ceremony," where a magical ring blooms flowers when touched by his destined wife. Therese is one of over thirty noblewomen chosen as a candidate.
Initially apprehensive, Therese's motivation shifts dramatically upon learning that all candidates receive a substantial advance payment (120,000 Pail for her family) and covered living expenses, regardless of selection. Recognizing her slim chances as an impoverished noble, she decides to pursue a stable castle job, such as a lady-in-waiting or aide, to secure her family's future. Her assigned knight, Jade Colic, a serious yet kind twenty-one-year-old, proves to be a crucial ally. Therese confides her true intentions to him, and he, understanding her practical goals, pledges his full support, promising to help her study and navigate castle life.
Upon arrival, Therese observes the cutthroat social dynamics among the other candidates, particularly the arrogant Clarice Gailord, who leads a clique of bullies. Therese, guided by her mother's "Methods for Surviving in the Castle," avoids conflict and focuses on her studies with her loyal family servant, Mabel. She frequently visits the castle library, a rare resource for her, to acquire the knowledge needed for a bureaucratic role.
A turning point occurs during a music concert hosted by Dowager Grand Duchess Sophia. Therese, playing her heirloom flute, wins an "Excellent Prize." More significantly, she witnesses Clarice and her group bullying Riina Belche, a talented twenty-year-old commoner official who also won an award for her harp performance. Disgusted by the injustice, Therese intervenes, scaring off the bullies. Riina, grateful and impressed by Therese's character, insists on repaying her. Therese, recognizing Riina's intelligence and talent, asks her to become her companion and tutor, helping her prepare for a castle position. Riina accepts, and their friendship blossoms.
As they study together, Therese learns about Riina's seven-year unrequited love for a mysterious blonde, blue-eyed boy named Noel, whom she met in the castle courtyard. Riina insists Noel's face was different from Grand Duke Leon's, despite the similar features. Therese, now supported by Mabel, Jade, and Riina, is actively pursuing her goal of securing a permanent job at the castle, transforming from a passive recipient of fate into an active agent shaping her own future within the complex political and social landscape of Accloud.
