Choi Sangeun gives customized marriage contracts for singles needing a marriage. After 13 years in the business, she wants to retire but finds it hard to end it with Jeong Jiho, a long-term customer of Mon, Wed, and Fri. They’ve been together for 5 years, but she knows nothing about him and delays ending their contract. Meanwhile, superstar Kang Haejin moves in the top floor of Jiho’s house...

Sangeun's hurt by Jiho asking to end the contract first. She delays it giving a flimsy excuse. She's strangely upset with him and is confused by it. Meanwhile, Haejin sees his first love Sangeun who disappeared 13 years ago after leaving a strong impression but is shocked she is Jiho’s wife. To make the matters worse, he witnesses Jiho’s strangeness and believes that she is in danger...

Sangeun, Jiho, and Haejin have a three-way encounter at the mansion. Jiho reveals his identity to Haejin due to his suspicion. Sangeun gets to know Jiho a little bit more but despite what she wants the time to end the contract comes. When the contract ends, restless Sangeun visits Jiho with divorce papers as an excuse to see him but is attacked by a mysterious armed man.

Sangeun's surprised at Jiho giving her concert tickets, not divorce papers. They extend their contract as they run into his senior judge and his wife. Madam Yoo Miho is in big trouble after seeking a comeback after losing everything 13 years ago due to Sangeun. Sangeun saves her and give up her retirement despite her love-hate relationship. Meanwhile, Haejin gets into trouble from a false rumor...

Sangeun is angry at Haejin. Haejin asks Sangeun to take him as her customer. She is torn seeing him vulnerable and eventually, she accepts his offer. Jiho feels uncomfortable about their contract. Sangeun tries to clear up the misunderstanding but is not easy. Meanwhile, Madam Yoo is released from the detention center and stays at Sangeun's, and their uncomfortable living situation begins...

Sangeun needs to settle a contract with Haejin. After some quarreling, Jiho's day is Mon, Wed, and Fri and Haejin on Tues, Thur, and Sat. And the alternate day marriage begins. Meanwhile, Sangeun and Jiho prepare a housewarming party for his work. While decorating the house they develop feelings. At the housewarming party, Sangeun drinks too much and gets a serious blackout the next day...

Sangeun remembers her first kiss with Jiho but is upset as Jiho seems indifferent. They hide their feelings causing their relationship to be awkward. As Haejin uses work as excuse and goes on a date with Sangeun, his feelings towards Sangeun grows even more. Meanwhile, Madam Yoo visits Ina group and threatens to take back Sangeun into their family again…

Jiho tries to find a way to express his feelings toward Sangeun. During a couple’s golf gathering, he doesn’t hold back to show kindness and care towards Sangeun causing her to have mixed feelings about him. Meanwhile, Haejin happily waits for Tues, Thurs, and Sat but gets into a big fight with Choi Ranhee who questions about Sangeun. He then collapses in front of Sangeun due to extreme stress.

Sangeun meets Jeong Jieun, ex-wife of Jiho and a legal advisor of Haejin. Jiho says no more than there’s nothing between them, but Sangeun’s thoughts gets tangled. After filming, Haejin misses Sangeun and visits her, but drunk Jiho appears and three of them have an awkward gathering at the beach. When Jiho witnesses Haejin and Sangeun being close, he appears to be bothered for the first time…

Jiho and Sangeun realized their feelings for each other, and he surprises his co-workers by coming to work very differently than usual. Sangeun tries to end the contract with Haejin to focus her relationship with Jiho and Haejin tries to give up his feelings for her but finds it difficult. Meanwhile, Jieun finds out Sangeun had contracts with both Haejin and Jiho and visits Jiho’s house…

Sangeun worries about Jiho as she is exposed to the public. Jiho’s senior informs about his promotion but doesn’t tell Sangeun. Sangeun tells Gangjin group’s family she doesn’t want to marry Haejin. Jiho makes questions for Sangeun and they have a great time. While Haejin’s at the police station due to his clash with Sangeun’s stalker. Sangeun’s in shock when the stalker is revealed…

Sangeun’s 12th marriage is unveiled causing controversy and she insists she’s at fault to protect Haejin. She asks Jiho to have some space due to this. Jiho and Haejin is upset seeing Sangeun trying to bear everything. Jiho hears from Woo Gwangnam of Madam Yoo’s provocation to Sangeun and investigates her and Ina group. Haejin prepares a conference to squelch criticism towards Sangeun…

Sangeun rushes to the hospital in shock when she hears of a mysterious car accident. Jiho comforts her and they become closer. Haejin makes a formal announcement of his breakup with Sangeun. Chairman Kang Jin tells him to join Gangjin group. Kang Seonjin feels threatened and uses Sangeun to ingratiate himself with his father. Meanwhile, Jiho questions the car accident and starts investigating…

Sangeun looks for what she wants to do after her retirement and Jiho supports her. Haejin enters the Gangjin group where he shines causing a conflict with Seonjin. Sangeun visits Haejin as she’s worried about his sudden retirement, but Haejin purposely acts distant towards her. Meanwhile, Sangeun finds out that Jiho met Jieun to grant her a wish causing them to have a lover’s quarrel…

While Sangeun and Jiho have a lovely time dreaming of their future together, people ordered by Seonjin secretly break into Sangeun’s house. Haejin learns of this and tells Madam Yoo of Seonjin’s scheme to use Project Jamie. Madam Yoo decides to take all the blame to protect Sangeun and Jiho goes against his principle for the first time to stop her…

After that day, Jiho waits for Sangeun who didn’t turn up. Sangeun doesn’t have the courage and hesitates and Jiho returns to his cold self. The co-workers become more worried seeing Jiho being so emotionless. Meanwhile, Sangeun realizes her feelings through honest advice from Gwangnam and Madam Yoo…