Wasn’t it just a marriage alliance? How did the Crown Prince truly fall?

Shen Qingyu is a twenty-six-year-old Stanford law graduate and the only daughter of a prominent Jingbei legal family. Raised as the exemplary child, she has never deviated from her parents' expectations, leading a disciplined life without romantic entanglements. Her mother, Manlin Jiang, arranges a marriage with Pei Huaijin, the CEO of the Pei Group and heir to one of Jingbei's most powerful families. When Shen Qingyu refuses to return to China for the arranged meeting, her mother threatens to cut off her financial allowance. In a moment of rebellion, Shen Qingyu visits a San Francisco bar, an unusual setting for her, and consumes enough alcohol to lose her inhibitions.

While at the bar, Shen Qingyu is approached by three men who attempt to drag her away. Pei Huaijin, who is in San Francisco for business negotiations, intervenes. He identifies himself as the CEO of the Pei Group, intimidating the men into leaving through his authoritative presence. Despite his initial intention to remain uninvolved, he finds himself unable to ignore Shen Qingyu's distress. He takes her to a hotel, intending only to ensure her safety, but Shen Qingyu, still under the influence of alcohol and driven by a desire to break free from her "good girl" persona, seduces him. She challenges his masculinity, prompting Pei Huaijin to agree to spend the night with her.

The two engage in a passionate encounter. The following morning, Pei Huaijin leaves without waking her, leaving a note and a black card containing five million yuan. The note states that the payment is for the night and asks that they pretend the event never occurred. Shen Qingyu wakes to find the note and card, initially feeling shame and confusion. She attempts to dismiss the incident as a one-time mistake, unaware that the man she spent the night with is the same Pei Huaijin she is supposed to marry.

Shen Qingyu returns to Jingbei, where she is greeted by her family. Her mother informs her that the Pei family has invited them to dinner the following evening to formally meet Pei Huaijin. Shen Qingyu prepares for the meeting, viewing it as a necessary formality to appease her parents. Meanwhile, Pei Huaijin also returns to Jingbei. During a family dinner, his mother shows him a photo of Shen Qingyu. He recognizes her immediately as the woman from the previous night. Instead of rejecting the arrangement, he agrees to attend the dinner, intrigued by the prospect of seeing how the bold woman from the hotel behaves in a formal setting.

On the day of the dinner, Shen Qingyu undergoes a professional styling session, transforming her appearance with elegant makeup and a pale yellow dress. Her parents accompany her to the Pei family residence, known as Pei Garden. The atmosphere is formal and tense, with both families treating the meeting as a serious alliance discussion. Shen Qingyu maintains her composure, presenting herself as the dutiful daughter while internally grappling with the secret she shares with her prospective fiancé. The story concludes as they arrive at the Pei residence, setting the stage for the confrontation between their hidden history and the public expectations of their arranged marriage.