The story takes place in a parallel world equivalent to the European Middle Ages. Living in dire straits, all countries put their main energy on war preparations. Weapons, equipment and military resources are the top priorities of the country. Due to the lack of military resources, mercenaries have become a high-income occupation and a part of the The goal of people with ulterior motives
In such a world full of wars, in addition to the wars between humans, there are also monsters called "Apostles". This is also the main content of the story. The hero Gus is the representative of the mercenary group "Eagle Group". Because his friend Griffith betrayed the mercenary group, he sold his soul to the devil. , he also turned himself into the master of the "Apostles", known as the Hand of God. After that, he cruelly offered the former "Eagle Group" as a sacrifice to the "Apostles". After surviving, Gus has only one belief for the rest of his life, which is to avenge Griffith for his comrades. He turned into a "black swordsman" and started the journey of revenge.