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 Yōji, 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.
