Choi Kang Chi is half beast and half human and was adopted by a merchant named Park Mu Sol when he was a baby. Kang Chi possesses a unique power. Dam Yeo Wool is the daughter of Dam Pyeong Joon, who owns the invisible knife Moo Kwan and is also a patriotic warrior. Kang Chi and Yeo Wool meet and fall in love with each other. However, there is animosity between their fathers. Jo Gwan Woong is a traitor. He uses his power to frame loyal and upright individuals and line his own pockets. His criminal schemes are thwarted by Kang Chi time and time again. Therefore, he is determined to kill Kang Chi in various ways. Kang Chi is troubled by his identity but stands up for justice.