The Demon Lords

The Demon Lords (魔王たち) is the forty-second episode of the anime adaptation That Time I Got Reincarnated as a Slime and the eighteenth of the second season.

Synopsis
Clayman gets angry at Rimuru, who shows unexpected resistance. Meanwhile, the oldest Demon Lord, Guy Crimson and Demon Lord Leon Cromwell, in addition to Veldora's sister, Velzard, grow increasingly interested in Rimuru.

Summary
After Benimaru and his army departed, Youm and co. set off for Falmuth, Diablo in tow. Rimuru, brimming with positivity, begins preparations to attend Walpurgis.

Clayman receives news from Yamza on the deserted state of Eurazania. Irritated by this, Clayman dismisses Yamza and orders him to throughly investigate the area. Yamza concludes his report with Storm Dragon Veldora's resurrection. One of his men heard from a passing peddler that the Falmuth army's disappearance was caused by the evil dragon. Clayman is easily convinced by this and quickly brushes off any concerns he had of Rimuru being the culprit, unknowingly falling for said slime's ruse.

The following day, in Harpy Kingdom Fulbrosia, Demon Lord Frey is having her wings groomed by her attendants. Milim stands a small distance away with a listless look on her face.

We then get a flashback to the events leading to Milim's current state. It starts with Milim barging into Frey's office and showing off the gift she received from Rimuru. Frey, smiling at the girl, mentions that she also has a gift for her; it's a pendant. Milim pleased by this immediately tries it on, triggering its mind control mechanism.

Observing this, Frey calls out Clayman's name and the aformentioned person emerges from his hiding spot. Pleased with the success of his plan, he physically abuses the helpless Milim and takes out his grievances on her. Frey, internally disgusted by this, warns Clayman to not get them both killed by triggering Milim's self defense mechanism. Hearing this, Clayman's composure returns, and he evaluates the advantage Milim's support will provide him in the upcoming Walpurgis with a pleased look on his place, and threatens Frey not to betray him.

Next scene, Demon Lord Leon visits the residence of fellow Demon Lord, Guy Crimson. They discuss Walpurgis, the actions of other demon lords, and the revival of the Storm Dragon. At this point, Velzard, the older sister of Veldora joins the discussion and expresses her interest in the topic.

Leon informs them of the story going around about Veldora's seal being undone by the blood of the Falmuth soldiers, but Guy and Velzard were skeptical about this. Leon, too, was of the same opinion, sharing his theory that Veldora's seal was dismantled by Rimuru.

Guy takes the theory at face value and muses that Rimuru would have to be a demon lord to accomplish that. After a bit more talking, Leon departs, leaving just Guy and Velzard behind. Guy offers Velzard a spot in Walpurgis but she rejects, saying she's not interested, and leaves. Guy reflects on the contents of the discussion, excited for Walpurgis.

Characters

 * Guy Crimson
 * Leon Cromwell
 * Velzard

Locations

 * Ice Continent
 * Frost Palace

Adaptation Notes

 * Light Novel Volume 6: The Octagram Soars Brightly:
 * Interlude : The Demon Lords

Trivia
Information to be added later.