Princess Ja-myung Go is the story of Ja-myung and Ra-hee, who were born as princess in Nakrang Country in the same hour as half sisters. An oracle warns that one of two would save the country and the other would destroy it. Ja-myung almost becomes assassinated by Wang Ja-sil, the ambitious mother of Ra-hee. But miraculously, she escapes to Shandong Province at the last minute. Ja-myung grows up to be a top artist of the Artist Group in Shandong. She meets Prince Ho-dong and realizes that she was meant for him. She returns to Nakrang Country as a royal princess. Her return provokes the conflict over the right to the throne. She invents the Ja-myung-gogak System to defend Nakrang Country from the attack. She leads and turns the Nakrang Army into an invincible army after winning many battles. Afterwards, her life is threatened by Ra-hee and her mother, Wang Ja-sil. Ja-myung becomes furious at her half sister, Ra-hee, when Ra-hee marries Prince Ho-dong. Prince Ho-dong manipulates Ra-hee into destroying the Ja-myung-gogak System to strengthen his political position as a prince of Goguryeo Dynasty. Ra-hee is forced to pull out her sword to kill her half sister Ja-myung.