I Have a Devil System

"Master Demon King, welcome back." A group of people knelt down with loyal eyes, their right hands on their chests. It seemed like he was waiting for some instructions. "Ha, what's going on?" Who is the person in front of everyone, who can make the Six Demons, who are famous in this world, kneel to the ground so devoutly. Who is he and what kind of mission does he have? ! !