Gamer Kazuma dies in a freak accident, and is met in the afterlife by a crass goddess, Aqua.

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.

A low-grade goddess turned arch priest who works hard to acquire party trick skills, a disappointing arch wizard who can only unleash explosion magic once per day, and Kazuma himself, whose only redeeming quality is his good luck. Kazuma despairs over the completely useless party that's been formed.

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.

With debt looming over her, Aqua convinces Kazuma to accept a high difficulty quest to purify a lake, which doesn't require killing any monsters.

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

"I want money." After paying back the debt Aqua has racked up, Kazuma and Aqua's monetary situation grows even more dire. The party accepts a quest to kill helpless Snow Sprites and heads for the snowy mountains in order to escape from the stables during this winter so cold it freezes Kazuma's eyelashes solid.

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!