Hello, guys.
According to a news article, KBS decided to make a series "On-Dal" set in the
Three Kingdom's Era.

On-Dal was the name of a Koguryo general who died in the battle against Shilla
kingdom in 590. He was from common origions, very poor and so simple-minded that
everybody called him "On-Dal the fool," and even the king had heard about him
and used to say in jest "I will marry you to On-Dal if you don't stop crying
right now" to his young daughter whenever she cried. So the princess grew up
thinking about who On-Dal was and got to think that On-Dal wil be really her
husband.
When she was 16 years old, her father tried to marry her to an aristocrat. but
she insisted on marrying On-Dal saying "Father, Keep your promise to marry me to
On-Dal" Finally she was kicked out of the palace, and the only place she could
go was On-Dal's cottage where he and his old mother lived......(no more
spoilers)

If they don't change their plan, this will be the first KBS drama ever set in
the Three Kingdom's Era - Shilla, Koguryo and Baekje. Most KBS historicals have
been set in Koryo and Chosun era as you can see in the recently-updated Korean
Historical Timeline.

http://www.koreanhistory.net/drama/drama.html