Rimuru sends a delegation led by Benimaru to the Animal Kingdom of Eurazania, ruled by the Demon Lord Carrion, also known as the Beastmaster, to establish diplomatic relations after becoming indebted to him in the battle against Charybdis. A delegation from Eurazania is set to arrive in Tempest around the same time, but the Animal Kingdom is a very warlike nation, and Shion is enraged when one of the delegates, Suphia of the Three Beastketeers, makes a belittling remark toward Rimuru. The goal was a friendly relationship, but it takes no time at all for a fight to break out...

Tempest is preparing a feast in celebration of Rimuru's return home. Then a newcomer, the majin Myulan, arrives to scope out Tempest on the Demon Lord Clayman's orders, having joined up with Youm's crew as their military advisor in order to enter the nation. Upon arriving, she's surprised to see what a strong nation it is, but continues to talk with its citizens to learn more. Meanwhile, the king of Falmuth, who sees Tempest as a nuisance, conspires with the Western Holy Church in a plot to invade the monster nation.

Following Clayman's orders, Myulan ignores the words of Youm and Grucius, both of whom have fallen in love with her, and activates the Anti-Magic Area spell. At the same time, Reyheim also activates Prison Field. The double barrier prevents Shion and the other fighters of Tempest from fighting as well as usual, and they end up at a disadvantage in their fights with three Otherworlders. Benimaru tries to contact Rimuru, who still hasn't returned, but he can't even get in touch with him due to the barriers.

At the same time as the attack on Tempest, Rimuru is also under attack. With one look, Rimuru realizes that his assailant is one of Shizu's former students, an Otherworlder, and the woman then introduces herself as the strongest of the Holy Knights, Hinata Sakaguchi. Rimuru is backed into a corner when her Holy Field seals most of his magic. At the same time, Shion and Hakurou, whose magic has been sealed by a similar barrier, are backed into a corner by Shogo and Kyoya.

Rimuru faced grave danger in his battle with Hinata, but he managed to escape in the nick of time by using a doppelganger to take the damage while he rushed back to Tempest. Upon arrival, he found the city in a tragic state, engulfed by blood and smoke. Benimaru tries to capture Myulan, the top suspect behind this disaster, but Youm and Grucius stand in his way. Swallowing his rage and grief, Rimuru realizes who their true enemy is and calmly questions Myulan instead of punishing her.

In order to come to terms with his own negligence and revive Shion, Gobta, and his other fallen comrades, Rimuru reveals that he used to be a human. But his allies think nothing of it and accept him regardless, as if it's the natural thing to do. Filled with gratitude for the warm, accepting environment he's in, Rimuru turns his focus to the army from Falmuth. He entrusts Benimaru and the others to destroy the devices that are generating the enemy's Prison Field while Rimuru himself sets out to attack the advancing army and use them as nourishment to become a Demon Lord.

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.