It's great for Kazuma that he brought Aqua along with him, but unlike in a game world, much is missing from his adventurer's lifestyle. No money, no equipment, and even fighting the lowest ranking monsters is a hard-fought battle. That's when they decide to recruit new party members.

All of the weak monsters have gone into hiding since a leader of the devil king's army has settled in near town. Kazuma, who had been focusing on improving his skills, is stuck at a standstill. With nothing else to do, Kazuma tags along with Megumin's training, which consists of unleashing explosion magic into an abandoned castle.

Dullahan, a top leader in the Devil King's army, yet again appears at the city in a frenzied rage.

Kazuma and Aqua can't properly accept rewards from quests due to their mediocre party lineup, and are so destitute that even keeping wood on the fire is difficult. Kazuma comes up with a plan and visits a magical accessories shop run by a woman called Wiz.

The rampaging ancient weapon: the mobile fortress, Destroyer, is headed straight for Kazuma and party's city!