Choi Sang-eun 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 Jung Ji-ho, 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 Hae-jin moves in the top floor of Ji-ho’s house...

Sang-eun's hurt by Ji-ho 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, Hae-jin sees his first love Sang-eun who disappeared 13 years ago after leaving a strong impression but is shocked she is Ji-ho’s wife. To make the matters worse, he witnesses Ji-ho’s strangeness and believes that she is in danger...

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

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

Sang-eun is angry at Hae-jin. Hae-jin asks Sang-eun to take him as her customer. She is torn seeing him vulnerable and eventually, she accepts his offer. Ji-ho feels uncomfortable about their contract. Sang-eun tries to clear up the misunderstanding but is not easy. Meanwhile, Madam Yoo is released from the detention center and stays at Sang-eun, and their uncomfortable living situation begins...

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