Past Tense of Brave

In 2077 AD, the Demon King from another world came to the human world with his four kings, and introduced the concept of magic into a world originally full of Muggles. Roselia, one of the Four Heavenly Kings, created tens of millions of demons and recreated the confrontation between demons and humans. How could the 43 years of defensive war and all-out war on land, sea and air be too miserable? The flames of war have spread across the seven continents and four oceans, eroding the living space of mankind and changing the way of life of mankind.