“Got any jokes about the demon realm? Let’s hear one.”
“Isn’t the demon realm itself a joke?”
“Come on, it’s not that bad. At least the demon realm has a Demon King.”
“Oh, and we have a Hero, a Pope, an Imperial Marshal, an Archmage King, and a Knight King!”
“Yeah, those are all the nobles’ glory. What’s any of that to a grunt like you?”
“Fair enough. We’ll be grunts our whole lives, but demon soldiers are different.”
“Oh? How so?”
“They can rise all the way to become an archbishop of the Holy Church! Hahahaha!”
In the year 300, evil humans launched the First Eastern Crusade against the demon realm. The first Demon King fell, and the demons lost most of their territory, forced to retreat and defend what remained.
In the year 800, vile and despicable humans launched the Second Eastern Crusade against the demon realm. The second Demon King died in battle, and the demons were left with only a third of their territory.
In the year 980, unstoppable human armies forced the Rock Dwarves and Dark Elves into submission, and the demons lost their central industrial region.
In the year 1300, the supreme human army marched against its loyal Demon King’s domain. The demons, their minds now awakened, rushed to kneel and joyfully welcome the royal army...
“My jester, faced with such dire straits, do you have a plan to turn things around?”
“I do, but how about listening to me play a tune first, my dear Demon King?”
This is the story of a band keyboardist who transmigrates to another world, becomes the Demon King’s jester, and is forced to shoulder the responsibility of restoring the demon race.
(Note: The worldbuilding is complete, and there is already a map of the main continent. It draws on medieval Warhammer and Hero-versus-Demon-King settings. Music is just a bit of flavor; the story is really packed with political maneuvering. The early stages focus on keeping a low profile and unifying the factions, the middle on weathering pressure and striking back, and the later stages on pure wish fulfillment.)