Mark is a new pediatrician who works for his family hospital. He meets Jaebum when he is treating his son, and their first meeting is not very pleasant. But since then, Mark has been sensing a weird presence of a gentle-looking guy, which is not seen by anyone else. Later, he finds out that the guy has something to do with Jaebum and his son, which lead him to start to care for the family.

When the crown princess for the current crown prince of Joseon, Crown Prince Im Jaebum, was in the process of being chosen, Im Jaebum fell in love at first sight with someone that was not one of the candidates. But the worst thing was that someone was not capable of being a crown princess, or absolutely impossible to be one, because it was a male. However, true love beat the impossible. Even though his lover can only be a concubine, his love for many was given to him and him alone.