JSDF officer and self-described otaku Youji Itami is on hand in Ginza when medieval warriors and monsters pour out of a mysterious portal called the Gate, cutting down civilians before Japan's military drives them back. Assigned to lead a reconnaissance team sent through the Gate into the fantastical Special Region beyond, Itami earns the loyalty of Rory Mercury, a demigoddess who serves as apostle to the god of death, and starts building diplomatic ties with the region's elves and sorceresses. As foreign powers eye the Special Region's resources, his team's low-key negotiations become Japan's best hope for keeping the peace.