WARNING: The following contains spoilers for Episode 28 of That Time I Got Reincarnated as a Slime, now streaming on Crunchyroll.
In That Time I Reincarnated as a Slime, Satoru has come a long way since he got reborn as Rimuru Tempest, a little blue slime. By now, he's built an entire kingdom of monsters named the Jura Tempest Federation, a place where monsters of all races can live together in peace. Unfortunately, the young Federation's neighbors are getting a little antsy, and it looks like everything could come crashing down in catastrophe soon.
Rimuru Tempest has long since learned how to fight and survive in this isekai world, but now, as a world leader, he's been thrust into the political arena, and he can't just fight his way out of a sticky situation. For every ally he gains, he also makes an enemy, and all this is about to come to a head.
The Demon Spy in the Midst
Demon Lord Carrion of the Animal Kingdom is still evaluating his Federation neighbors, and he sent the battle-hungry Grucius and Suphia to test the waters where Rimuru's kingdom is concerned. The Beastketeers are welcome guests, observing every last detail of Rimuru's kingdom in action. So far, they like what they see, and Rimuru, princess Shuna and others are setting up formal trade agreements with the Animal Kingdom. All is well on that front, but Myulan is a whole different story.
Myulan is a powerful wizard who impressed (and gently defeated) Youm the champion with her earth magic, earning her a spot in his adventuring party. Though a welcome guest in the Federation, Myulan is actually a spy for Demon Lord Clayman, who has a very different agenda from Demon Lord Carrion. Clayman is plotting something, and Myulan's careful observations will lay the groundwork for whatever comes next. The longer Myulan stays in the Federation capital, the more danger Rimuru's young kingdom is in, and no one has any idea. Myulan is a catastrophe waiting to happen.
At least Rimuru is making inroads with the kingdom of Blumund, trading high-quality potions and other goods to Baron Veryard. By now, the Federation and Blumund are partners, and if one of them is attacked, the other will come to its defense. Rimuru is nervously realizing that his Federation acts as a buffer state for Blumund against its allies. Can the Federation survive being a shield for another kingdom? Time will tell.
Falmuth Opposes the Federation... and Has Its Own Isekai Warriors
By now, it's clear that many Earth denizens are being summoned to this world, with Rimuru and Shizu being the most notable. Shizu's five students are also Earth natives, and what Rimuru doesn't know is that the scheming kingdom of Falmuth has another trio of isekai heroes as a secret weapon. Right now, the Falmuth king and his advisors are anxious about the Federation's strength, and they want Rimuru's monster kingdom gone. Archbishop Reyheim of the Western Holy Church offers the entire Church's aid to launch a holy war, and all Falmuth needs is provocation from the Federation to justify an all-out assault on Rimuru's holdings.
This is where the new isekai heroes come in: they'll wreak havoc in the Federation, and once Rimuru's forces retaliate, Falmuth will have an airtight reason to strike back. Shogo, one of the isekai heroes, is spoiling for a fight while Kirara merely wants to find creature comforts in this new world. And all three of them long to return home, or at least free themselves of their thralldom to the Falmuth kingdom. They don't like this world's lack of modern comforts, and they really don't like being used.
At this point, Rimuru's main challenge has shifted from gaining legitimacy for himself to defending his entire kingdom from new enemies. The Federation's relationship to other realms mirrors Rimuru's attempts to make friends and impress new allies in Season 1. Rimuru and his followers have a lot to offer, but they live in a world that often doubts or fears them, so the risks are immense. Rimuru was never good at speeches or politics, but he better learn quickly, as King Gazel warned him, or Rimuru's brave new nation will face its doom.