Gil Dong fails the military exam due to his fight with villains. On his way back, he meets Yam Jeon. Bok Dol and Kkut Soon steal Gil Dong's clothes and impersonate a fake Hong Gil Dong, but are punished by Gil Dong and later join him. Master Yoon seeks help due to the demon Hwang Bo. When Gil Dong finds himself at a disadvantage in his fight against Hwang Bo, he flies to the modern world and, with the help of Dr. Kang's family, defeats Hwang Bo. Hwang Bo also calls for help from the demon leader Tung Ga, and Gil Dong begins to fight Tung Ga. Unable to cope with Tung Ga, Gil Dong sees Yam Jeon and Kkut Soon taken hostage. After traveling between the modern and ancient worlds, solving various cases, and honing his martial arts, Gil Dong finally defeats Tung Ga's gang and rescues Yam Jeon and Kkut Soon.