Corporate worker Mikami Satoru is stabbed by a random killer, and is reborn to an alternate world. But he turns out to be reborn a slime! Thrown into this new world with the name Rimuru, he begins his quest to create a world that’s welcoming to all races.

Now that the Jura Tempest Alliance is growing even further, they will now be meeting the animal kingdom of Eurazania, reuniting with King Gazel, rising tensions between monsters and humans, and Rimuru encountering the strongest enemy he’s ever faced.

Rimuru has officially become a Demon Lord after defeating Clayman. Following Walpurgis, the Demon Lords' banquet, Rimuru's domain is expanded to include the entire Great Forest of Jura. Anticipating a flood of representatives from all races showing up to pay their respects, Rimuru decides to throw a festival to commemorate the opening of Tempest, using it as an opportunity to gain new citizens and present Demon Lord Rimuru to the world. Meanwhile, in the Holy Empire of Lubelius, home base of the monster-hating cult of Luminism, Holy Knight Captain Hinata receives a message from Rimuru. But the message is actually a fabricated declaration of war sent by some unknown party. Upon learning that Hinata is heading for Tempest, Rimuru makes a decision... Thus begins a new challenge for Rimuru, striving to distinguish friend from foe in his pursuit of the ideal nation where humans and monsters can prosper together.