Rimuru is building a dungeon in preparation for the upcoming festival. It will feature treasure chests containing weapons made by Kurobe, and Veldora will inhabit the deepest floor as the final boss. Then Milim suddenly shows up with a suggestion...

On the last day of the audience, Rimuru meets Momiji, the representative of the Tengu clan. Their meeting comes after Rimuru had sent Benimaru to the Tengu village to request their permission to build a tunnel through the Kusha Mountains.