Choi Kang Chi is half-beast and half-human and was adopted by a merchant, Park Mu Sol, when he was a baby. Kang Chi possesses a rather unusual 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 one another. However, there is animosity between their fathers. Jo Gwan Woong is a traitor. He uses his power to frame loyal and upright individuals and to line his own pockets. His criminal schemes are thwarted by Kang Chi time and time again. Consequently, he is determined to kill Kang Chi by various means. Kang Chi is troubled by his identity but stands up for justice.