For 15 years, a war has raged between the humans and demons. The human's greatest warrior, Hero, heads to the castle of the Demon King, leader of the demons to end the war. To his surprise, the "Demon King" is in fact a woman and she has been waiting to meet Hero in person and wishes to talk with him instead. As they talk, she reveals the war has actually benefited both sides as their races have put aside their differences to fight against a common enemy and improved the economy. However, it has allowed the powerful and corrupt to abuse the weak particularly how the poorer Human Southern kingdoms must continue fighting the demons in exchange for food and financial aid from the rich Central kingdoms. Furthermore, no matter which side wins or if the war suddenly ends without compensating those employed because of the war, it will lead to a massive civil war much to Hero's horror. But the Demon King has a plan to bring prosperity and a lasting peace for both their races and wants his help. Convinced, Hero agrees where both of them pledge their lives to each other.