Kazuma thinks of a way to stay in the capital for Iris's sake, and declares that he will capture the thief who's causing a stir in the streets! Since the thief targets nobles with bad behavior, Kazuma and his friends decide to stay at Alderp's mansion.

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 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.

Kazuma has crashed Darkness's wedding to Aldarp and pays him the two billion eris he says he's owed. Aqua and Kazuma try to make off with Darkness but Aldarp won't relinquish her so easily and orders his guards to stop their escape.