Humans with strange new powers have begun to appear. They are called Knockers. The Knockers are not without rival, they are being hunted by the mysterious being named Void! Not adhering to any notions of good or evil, Void pursues the Knockers while being himself in the cross-hairs of government agencies BOOTS and the Public Safety Commission Section 5, along with mysterious pursuers like Shamonji the beautiful swordsman and the undead soldier Pale Horse, who arisen from the dead. Just what is Void's goal, and for what purpose does he stretch his raven wings?

1895. Mok is the son of a Cho-Sun noble. While accompanying his father to the capital, he sees a strange man without feet. Back home, he becomes severely sick. The mysterious man, who is none other than a ghost, guides Mok through his fever and reveals to him that he's protected by four divine spirits. Mok learns that he is gifted with the ability to see the world of spirits and ghosts. Since then, whether he likes it or not, Mok intervenes to settle spirit-related phenomenona...