Youji Itami, an otaku and off-duty officer of the Japan Self-Defense Forces, was on his way to a doujin convention in Ginza, Tokyo when a massive gate-shaped portal emerged, unleashing supernatural creatures and armored warriors who rampaged through the city, leaving death and destruction in their wake. Youji sprang into action, saving as many lives as possible while his JSDF colleagues battled the invaders. Three months later, Youji was tasked with leading a special recon mission as part of the JSDF's mission to the "Special Region" beyond the gate. They must venture into this unknown realm to gather intel on their new foes and establish peaceful relations with the ruling empire. Failure means plunging headlong into a catastrophic war that could engulf both worlds.