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.

Kazuma runs into some adventurers he knows while out for a walk and decides to go with them to a shop run by succubi said to show its customers enticing dreams.

Kazuma and the gang fail to defeat the hydra in the lake near Axel. The gang hopes to rely on knights from the capital, but they've been delayed due to a bandit disturbance for which a bounty has been issued. Darkness, however, is obsessed with the hydra.

Darkness's wedding to Aldarp is imminent. Despite Aqua's and Megumin's pleas, Kazuma has no intention of intervening. Vanir then visits the mansion and reveals a shocking secret to Kazuma.