The protagonist, Xu Bo, is a man who lost both his parents as a child and relied on his younger sister, Xu Yan, for companionship. By chance, he joined the military and grew into a formidable warlord. During an operation in Afghanistan, he accidentally killed his teammate and sworn brother, Yuan Qin. As he lay dying, his friend entrusted Xu Bo with the care of his younger sister, Yuan Xin, and younger brother, Yuan Le. Forced to retire after returning to his unit, Xu Bo went home to care for his own sister and his friend’s family. But things did not go as smoothly as he had hoped. He had no choice but to join a mercenary outfit and become the feared leader of the Black Blade mercenaries.
