The Hero defeated the Demon Lord, and peace arrived.
"Hurrah for the Hero!"
"Hurrah for the Saint!"
In the royal capital a parade was held, and they were welcomed with great fanfare.
"Hero, sir, you're wonderful!"
"Uh—yeah."
And so marriage to the princess was granted, and the Hero Cowl happily wed her.
The lavish banquet staked the nation's prestige.
Delicious dishes were laid out wall to wall.
First-rate wine and fish, meat and fluffy bread.
Everything, they say, was magnificent.
The aged Takuya put his knowledge of Earth to use and, together with Cowl, developed the nation.
But Takuya, too, would come to rest beneath this land without ever returning to Earth.
"Whew. One chapter closed—but the trouble starts here. Eh, Aithel?"
"Lunga, so it does."
"The decline of the kingdom."
After the transported former Hero was gone, the reign of the Hero Cowl began.
But the realm sinks further and further into decadence.
With the Demon Lord's army no longer attacking, military mobilization ceased and everything went slack.
Cowl could only watch as the nation crumbled from the ground up.
In despair, he too departed for heaven.
By this point the realm had fallen so far you'd think it had been better off developing during wartime.
The sewers they'd built went unmaintained and fell into disrepair.
The national army couldn't muster even a proper fighting force.
And that's when the surrounding nations rose to prominence.
They had watched the Demon Lord subjugation from the sidelines and long envied the kingdom's prosperity.
The neighboring countries greedily adopted the latest technologies and worked desperately to enrich themselves.
One thing and another, and the kingdom's international standing was slipping away, the neighbors throwing their weight around while skirmishes dragged on at the borders.
Still, being humans against humans, the wars stayed half-hearted and never settled for a long, long time.
Several centuries on.
As for ancient ruins, elven sites over a thousand years old are sometimes excavated.
But the ruins of the developed cities from the Demon Lord subjugation era could also be seen here and there.
It's only natural there'd be rumors that the buildings and institutions back then were finer than today's.
The Sage who served the Hero is said to have been an elf.
Beautiful and wise, by all accounts.
Being of a retiring nature, she never took the spotlight—but she is said to have been a great benefactor who brought much of the elves' advanced culture into the human world.
"Well, Earth had ancient Rome and the like too."
"So it did."
The people of the kingdom gaze curiously at the tall ruins at the excavation sites.
"This one's another baffling ruin—we've confirmed identical structures scattered all over the place."
"Identical, you say. Are they really the same?"
"Yes. I've seen several of the actual things."
"Hmm."
The scholars cock their heads in puzzlement.
"Say, Lunga."
"What?"
"What is this?"
"Uh—ah, well—that's an oxygen generator. A paid item, that one."
"Er... that's you meddling with the surface, then?"
"Mm. Early on, the cyanobacteria alone seemed to be struggling, y'see."
"Honestly, always reaching in like that."
"Sorry."
"And what's more, you left it running—it's still going even now, isn't it."
"Oh—it really is."
The device was still alive and well.
With it, it goes on churning out oxygen and carbon compounds from carbon dioxide, day after day.
"Good grief."
"Ahaha."
Well, when I made the elves I brought in a forced-evolution device too, so surely a little of this is fine now and then.
We're gods anyway, and we can do whatever we like with this world.
In that sense, maybe we're objects of terror as well.
Now then—several more centuries passed, and a thousand years were about to elapse since the first Hero.
It's two thousand years from ancient Rome to the present day, so as human history goes this is on the short side.
"The equipment from the ruins era is astonishing."
A certain scholar says, gazing at the ruins.
Some of them are the gods' ruins, so it's hard to say—but in truth there were fields where the past really did have the higher technology.
"Magic tools have advanced too. We keep finding devices we can't make sense of."
Some of these are applications of the otherworld technology the Hero Takuya proposed.
Electric fans, heating and cooling, hair dryers—that sort of thing.
Now and then something odd gets dug up, and it leaves them wondering.
"The elves might know something, but..."
"Those lot are secretive."
"Well, quite. And the humans treat them coldly, which only makes things worse."
"No doubt."
The excavation crew's engineers throw up their hands in surrender.
The elves say they saw it all with their own eyes, yet they tell you almost nothing of the substance.
The elf who once kept company with the human said to have been the Sage passed away long ago, I'm told.
To begin with, though some tribes still carry on the pure elven bloodline even now, a fair number of elves are of mixed blood with humans, and many are half-elf or less.
There are no statistical figures for average lifespan, but there was a paper suggesting it may be dropping year by year.