The world was ruled by the dragon Overlord, who possesses great power. However, a brave young Hero brought an end to his reign. "I do not want to take your life," The Hero cut off one of the Overlord horns which is the source of his power. After that, the Hero return to the lonely Overlord, who was healing in solitude, and spoke to him. And to the days spend with the Hero, the terrifying Overlord gradually grew more peaceful, and eventually, he and the Hero became close friends. One day, the Hero appeared before the Overlord with a life-threatening injury and said, "Please raise my daughter well in my stead, for I will soon die." In his arms, he held a baby. "It is for this moment that I was able to survive," the Overlord thought. After, the Hero's daughter was raised by the "King Dragon" and former Overlord. Hearing about her father's adventures from the King Dragon, she too longs to become a hero. The time had come, the King Dragon thought. He would raise the girl to become a noble hero like her father. —Even if she has to defeat him one day.