The military fantasy series begins when a gate appears in Tokyo's Ginza district sometime in the 21st century. From the gate pours out monsters, knights from middle-age Europe, and other fantasy-like beings, and they kill many of the citizens of Tokyo. This event is known as the Ginza Incident. The government sends a small group of soldiers from the Japanese Self-Defense Forces (a replacement for Japan's military) to the alternate world beyond the gate. Led by otaku soldier Youji, they find that