To put a stop to Clayman's plans, Rimuru uses transport magic on a large scale to both move Tempest's army to Eurazania and evacuate the people of Eurazania to Tempest. Rimuru also decides to crash Walpurgis, the Demon Lords' banquet, in order to settle the score with Clayman personally. Since this will be a return match for Shion, he decides to take her and Ranga along. New military forces are organized in Tempest in preparation for the battle against Clayman's army. At last, the eve of battle is upon them...

Benimaru leads his army to Eurazania, and Youm heads to Falmuth to take it over along with his buddies and Diablo. Rimuru succeeds in outwitting Clayman by transporting all of Eurazania's refugees to Tempest. Since Clayman has been striving to evolve into an Awakened Demon Lord for a long time, his resentment toward Rimuru grows. Meanwhile, Demon Lord Leon, Veldora's sister Velzard, and Guy, the oldest of the Demon Lords, become increasingly impressed with Rimuru.

Rimuru continues with preparations for Walpurgis, including making Treyni evolve into a Dryas Doll Dryad. Meanwhile, Benimaru and his forces have arrived in Eurazania via transport magic, and they promptly run Clayman's army into a trap set by Geld. The Three Beastketeers, determined to rescue Carrion, set out to subdue the enemy army's leader. Albis fights one-on-one with Yamza of the Five Fingers, while Phobio takes on Footman and Tear.

Gabiru narrowly wins his battle against Hermes. Watching their outcome is Middray of the Dragon Faithful, whose skill was enough to overwhelm even Suphia. Though he looks like a human, he is actually a Dragonewt like Gabiru. Meanwhile, Yamza uses his artifact Doppelganger to create a double of himself, but Albis still defeats him soundly. He tries to surrender, but Clayman takes control of him and forces him to transform into Charybdis.

Clayman tries to convince the other Demon Lords that Rimuru should be purged, but Guy tells him that if he is truly a Demon Lord, he should defeat Rimuru himself. What should be a one-on-one battle between Rimuru and Clayman is joined by Milim, who has been brainwashed by Clayman, so Rimuru takes on Milim while Shion faces Clayman. But Rimuru is at a disadvantage against Milim and finds himself pushed back... until Veldora bursts onto the scene and takes Milim's attack in Rimuru's place.