The Devil King's army attack alarm rings in the royal capital! The adventurer's guild calls on high-level adventurers to join the battle. Having failed to capture the thief at Alderp's mansion, Kazuma joins the fight in order to redeem his reputation.

Kazuma and his friends return to Axel and receive 300 million eris as a reward for subjugating Sylvia, an executive of the Devil King's army. Kazuma and Aqua go to high-end restaurants, and Aqua enjoys her long-awaited life as a celebrity.

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.