Five demons have waged war against humanity, destroying more than half of the nation's territory. To bring a temporary ceasefire to the conflict, a political marriage is arranged between the Duke’s daughter, Cecilia, and the Demon King—the very individual responsible for the greatest slaughter of humans. Cecilia intends to seduce and ensnare the Demon King to prevent the extinction of mankind, but it turns out the Demon King hides a massive secret...? The award-winning work from the NovelUp+ Original Contest! Akio Kawada, author of 'Ura Har', delivers a brand-new beautiful girl battle fantasy!!