The Little Boy Swordsman.

Just after the Japanese attack on Joseon in the late 16th century, Bak Seong-dal, a magistrate of the Dong-nae, Busan conspires with a Japanese spy and kills his political rivals Lee Won-guk and Yoo Cheong. Ten years later, Cheong-myeong, 12 year-old son of Lee Won-guk who survived the killing, seeks revenge on Seong-dal. Jeong-a, daughter of Yu Cheong who also survived, trains in martial arts and sets out to find her enemy, too. Cheong-myeong and Jeong-a, who were betrothed when they are children, join together to kill Bak Seong-dal.