Original: 완벽한 결혼의 정석
Waking from a fatal accident to find herself in the past, Han Yi-joo teams up with Seo Do-guk to take revenge on the family who never loved her.
Yi-joo is perceived as a gentle soul, selflessly putting others first. However, the disrespect she endures is far from what she deserves. Her longing for a family leads her down a path of righteousness, but everything crumbles at the Han Gallery Charity Auction. Faced with unspeakable horrors, a fatal accident befalls her, and in her dwindling breath, she prays for a chance at redemption.
Having realized that she's returned to a point before her marriage, Yi-joo decides to navigate a different life course. Her stepmother and stepsister, no longer considered part of her familial circle, morph into her most formidable adversaries. She initiates the process by breaking off the wedding with a man more inclined toward her sister, and then she orchestrates a scheme to sow intricate chaos within her supposed family.
It's only through reading an article about a small incident in the park with Do-guk that Yi-joo uncovers his ulterior motive. Confronting him, she presses for an explanation, and to her delight, it turns out to be quite heartwarming. To add to the surprise, Do-guk proposes that she reside in his house, minus his presence. Feeling a sense of dependability, Yi-joo cherishes the moment, unaware of the uncertainties ahead.
The next phase unfolds in Yi-joo and Do-guk's contractual marriage as their families meet for the initial discussion regarding their impending union. Jeong-hye remains oblivious to Yi-joo's orchestration and her amazement deepens when Yi-joo presents one of her replicas as a surprising gift. Despite the surface portrayal, Yi-joo employs stern language with Do-guk, reminding him not to cross boundaries in their feigned marriage. Do-guk struggles to mask his evident disappointment.
The day after the incident at the ferry port, Yi-joo learns that Do-guk is dealing with a panic disorder. Believing that Jung-wook holds crucial information about Do-guk's condition, she arranges a meeting with him, going against Do-guk's explicit request not to meet him. Despite her worry for Do-guk, he sternly warns her not to cross the boundaries of their contractual relationship. Seeking comfort, Yi-joo visits her grandfather and encounters an incredible story about her birth.
Yi-joo comes close to a regrettable choice at her wedding with Do-guk, driven by the realization of Jeong-hye's manipulation, but Do-guk intervenes just in time. The morning after the wedding, Do-guk discovers a note from Yi-joo and her empty room. Meanwhile, Yu-ra views Jung-wook as an ideal instrument for her schemes.
Even though it all began as a contractual arrangement between Yi-joo and Do-guk, her sentiments for him evolved over time. On the flip side, Yu-ra and Jung-wook seem on the verge of establishing their own agreement driven by sheer greed. Their sinister intentions promptly take shape as they expose the confidential contract between Yi-joo and Do-guk to the entire family.
Now that the secret pact between Do-guk and Yi-joo has come to light, the entire family is rife with disappointment and demands for justification. Jung-wook seizes this moment to press Do-guk even harder, but Do-guk appears to be one step ahead in every move. Meanwhile, Yi-joo's plan faces unexpected disruptions as rumors about her begin circulating and spiraling out of control.
With Jin-woong in the hospital, Jeong-hye declares herself the new interim chairman of Hanul. With plans to make her position permanent, she starts trying to win over shareholders. However, Yi-joo is onto her plan and starts doing the same. Meanwhile, Jin-woong becomes aware of Yi-joo's identity and starts to suspect Jeong-hye.
Jeong-hye's plans to take over Hanul for good fail as Chairman Han Woon-jae, Yi-joo, and Yi-joo's birth mother speak against her at the shareholders' meeting. Meanwhile, Yu-ra discovers that she is pregnant with Jung-wook's child and that Yi-joo is Jin-woong's biological daughter. She slowly comes to realize that her perspective of reality has been wrong all along.
Cho Dong-soo rats out Jeong-hye to the police, and they both get arrested. Yi-joo and Do-guk seem to enjoy their lives until Do-guk confesses that he is the reason why they both came back in time. Meanwhile, a construction site worker hired by Taeja's subcontractor dies on the job. Jung-wook tries to sweep things under the rug.
Jung-wook breaks out of jail and kidnaps Yi-joo in an attempt to torment Do-guk. However, Do-guk is determined to save Yi-joo from the same fate that made them go back in time that fateful day, even if it means risking his own life to do so. As their repeated time draws to an end, Yi-joo and Do-guk feel unsure about what will happen in their future. Will they find happiness and peace in the end?
