Chapters 3 through 12 of the light novel detail the protagonist, Fine Shelter, receiving a mysterious card stating "I know your secret." Fine, the third daughter of a Count, finds the card on her desk, a breach of the household's strict delivery and security protocols. She has no idea what secret the sender might know, as her life, though somewhat distant from her family, has been uneventful and open.
Fine reflects on her upbringing. Her parents, the Count and Countess, were consumed by the chaotic energy of her two older brothers, Klaus and Karl, and later by the delicate health of her younger sister, Alicia. As a result, Fine was largely raised in a separate wing of the mansion, receiving ample care from staff but little direct attention from her family. This led to a feeling of being overlooked, though not mistreated. She found solace in a family portrait and her nightly goodbyes to it.
A turning point occurs when Fine is eight years old. Her brothers have finally settled down, and Alicia has recovered. The family decides to have a new portrait painted, and for the first time, Fine is brought into the main house and included in family meals. However, she struggles to address her parents and siblings directly, highlighting the emotional distance that had developed. This realization deeply affects her parents, who acknowledge their neglect. They begin to actively include Fine, leading to a period of adjustment for the entire family, with her siblings now doting on her.
Later, Fine becomes engaged to Darius Reiner, the third son of a Marquis. Darius is a "God-Reborn," possessing immense magical power that manifests based on his emotions. His uncontrolled magic led him to become withdrawn and emotionless. The engagement is initially a political arrangement, but Darius had fallen in love with Fine at first sight when he saw her as a child. He had even joined the Shelters' knight order as a commoner to be near her after a misunderstanding with his father about his desire to marry her.
The mysterious card is eventually revealed to be a prank by Darius. He had learned that Fine hums a peculiar tune, "Fuhunga," when she is deeply focused, especially when embroidering or drawing. This humming is linked to her own latent "God-Reborn" ability, which causes her drawings to animate. Darius, having recently mastered normal handwriting and wanting to share a secret with Fine, sent the card. He had observed her humming and her happy expression while working on her wedding dress, realizing this was a "secret" he alone knew.
The chapters culminate in Fine and Darius's wedding. During the ceremony, Fine's wedding dress, adorned with embroidered jasmine flowers, animates due to her strong emotions, filling the venue and town with singing flowers. This grand display of her ability, a secret she had kept hidden for years, is her heartfelt confession of love to Darius, who reciprocates her feelings. The story ends with Fine embracing her unique abilities and her newfound happiness with Darius.
