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 to the alternate world beyond the gate.
Led by otaku soldier Y?ji, they find that the villages in the world are being attacked by a dragon.
An elf girl who is a survivor from the dragon’s rampage joins the group in their travels across the dangerous new world.