Kim Mingyu, a brat you met one day, who turns out to be your... in-law!?

Your sister, Ha-Yoon, wanted to get married with the love of her life. Being the only family member of hers, you decided to support her and even planned to buy her a wedding gift.

But finding the gift for her wasn't easy. You started to search for the perfect gift for her online, and guess what? You found it. You decided to meet the seller in a cafe, face-to-face, to see whether the stuff you wanted to buy is authentic.

You finally met him. A tall, muscular guy, who's very, very handsome, but had such a bad attitude. After some negotiations, you cancelled from buying the stuff from him because of his behavior, and decided to give your sister something else instead.

A few days later, you and your sister had a family meeting with your sister's fiance, Minho—just the three of you, though, because Minho doesn't have any family members either. Suddenly before you three could start eating, someone walked in, Kim Mingyu, the guy you met a few days ago—the damn brat. Turns out Minho has a younger brother who he hadn't met for years.

Things lead to other things, Mingyu and Minho fought. Mingyu left and you've never heard from him anymore, even after your sister's wedding.

Three years have passed. Ha-Yoon and Minho were living as a perfect, happily married couple. They even have a two-year old son named Woo-Joo.

One day, you got a phone call from the hospital, saying that Ha-Yoon and Minho had a car crash, which has taken both their lives—except Woo-Joo, who miraculously were safe and only had a little injury.

You met Mingyu again at the funeral. Being too busy and tired, you accidentally injured yourself, making it hard for you to take care of Woo-Joo. Because of that, Mingyu had to help you to take care of Woo-Joo—until you're fully recovered, even though he didn't want to take care of Woo-Joo, he didn't even want to claim that kid as his nephew.

One thing leads to another, Mingyu is now living with you in your late sister's and brother-in-law's house with Woo-Joo. He had to. The house he was planning to stay in had a little problem, causing him to live with you for a while.

It wasn't easy. You two would always bicker. Despite that, you two had come to an agreement where Mingyu had to take care of Woo-Joo (and the house) while you were working. Only for a month. Only until his new house is ready.