My Sister-in-Law is 19

A romantic comedy about two future 19-year old sisters-in-law!

A thrilling story of youngsters trying to realize their small yet significant dreams! Because Kang-pyo needs a monthly treatment for his heart disease, they go to a hospital in Seoul every month. The thought of going to a hospital is very exciting for Yu-min since she sees her prince charming, Min-jae, who is a resident doctor at the hospital. Yu-min has had her eye on him for almost a year. Almost like a cute stalker, Yu-min stays close to Min-jae. Finally, she decides to pretend to be a student at the university that Min-jae attends.

Although she feels guilty about lying, Yu-min now has more chance to see Min-jae outside of the hospital. Min-jae's mother forces him to get engaged to a daughter of the CEO of a car manufacturing company, so that her business can benefit from it. To free himself from his mother's constant requests, Min-jae offers Yu-min a part-time job as pretending to be his fiance until the girl he loves returns to him. However, Min-jae finds out that Yu-min is still in high school, and most surprisingly, in the same grade as his younger brother, Seung-jae.

This series is about a 19 year old girl, Yoo Min who was being abandoned after the death of her mother. She lives alone with her adopted brother, Kang-Pyo. She accidentally meets Seung-Jae, the younger brother of Min-Jae. By chance, Yoo Min actually had a crush with Min-Jae, a doctor who treats her brother illness for a long time.

To fight off his mother demand, Min Jae gets in an engagement contract with Yoo Min and they all end up living at Min-Jae's house. Unexpectedly, Yoo Min and Seung-Jae are going to the same high school.

From there, Seung-Jae secretly loves Yoo Min. On the other hand, Yoo Min's father who got amnesia from a car accident is looking for her again after 15 years old she had been abandoned by her neighbors. The conflict comes when the people who living in Min Jae's house are actually related to Yoo Min's abandonment. They are the neighbours who stole the inheritance and abandoned her when she was four year old.