Same Age Aunt.

Ja-hyeok, who was born into a family of doctors and is forced to go to medical school, failed the entrance exam and is trying again. Mi-yeon, Ja-hyeok's stepmother, who is married to his father, goes on their honeymoon. While the couple is away, Mi-yeon's younger sister, who is the same age as Ja-hyeok, decides to tutor him.