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“Once a magical civilization advances this far, you can’t really tell it apart from science anymore.”
“Both are just things people refine for the sake of living comfortably,” Fumitsuki replied. “In a world where magic is normal, even something like a communicator would look like magic.”
“In the end, it all depends on what kinds of laws are baked into that world.”

Fumitsuki, Lullus, and I had arrived in a crumbling world, half-ruined. From the perspective of a world without magic, nothing here made any sense. Houses that seemed to stand on shapes so impossible you’d think they were balancing on a needle. Towers twisted so strangely that they blatantly ignored physics. Giant clocks floating in the sky. Massive barriers cover entire towns. The flying cars didn’t run on engines. Inside them were magical catalysts. Even though the towns were large, hardly anyone walked around because transportation magic and other conveniences were so advanced that people in a hurry simply didn’t bother with roads.

The norm was teleportation. Walking was for when you felt like it. Vehicles were basically for entertainment. That was this world.

“Even though it’s this prosperous, everything outside the barrier is just sand,” Fumitsuki murmured.
“There are also rocks, and monsters whose diet no one understands,” I said.
“You don’t need to mention the smallest details,” Fumitsuki complained, cheeks puffed.

I ignored her. There really were rocks. And monsters. In this end-of-the-world sort of place, towns like this survived only because of their barriers. People didn’t seem desperate, though, thanks to teleportation, they didn’t actually feel trapped.

Since neither Fumitsuki nor Lullus stood out here, we wandered through town. I wondered idly whether the people in charge realized the world would collapse soon. Eventually, we came across a museum.

Its name, “Museum of the Legendary Ancestor.”

“It says they defeated a god,” Fumitsuki said. “But was it really a god?”
“By our standards, it was a Demigod,” I replied. “And this legendary ancestor of theirs was a reincarnator from another world.”
“A reincarnator? Like, born again with their memories intact?”
“Yes. And they even met a god once. A proper reincarnator of pedigree.”

I, on the other hand, was transported first, then reincarnated, decidedly not a proper reincarnator.

If this guy died in a truck accident in his previous life, he’d practically hit the jackpot cliché. If it were a case of the god accidentally killing him, then you could add bonus points. Gods could accidentally kill people. It was not impossible, and they could reincarnate them afterwards, which was not impossible either. Whether the world could withstand it was another matter.

“So did he get some special ability?”
“What he received was less a cheat skill and more a talent. A very impressive one, yes, but something someone born in this world could also theoretically acquire.”
“But he defeated a Demigod, right?”
“He did.”

It wasn’t a riddle, but Fumitsuki still tilted her head and started thinking. Lullus answered first.

“I believe the correct phrasing is that the people of this world could not defeat it.”
“There are many types of Demigod,” I said. “Some can actually be killed by humans, though usually it requires layers upon layers of preparation just to make the attempt plausible.”
“Then… was it really okay to kill it? Aren’t Demigods sent by gods?”
“I became a Demigod mostly because I happened to be compatible with the role.”

I was supposed to just die peacefully, but apparently that made me an appealing candidate to pick up. Life was unfair. If only I’d died full of hatred for my classmates, I could’ve slept forever.

“So they picked the wrong person to make Demigod?”
“Either the god chose wrong, or the Demigod changed partway through. At any rate, it became harmful to the world, or rather, to people. Let’s peek inside the museum.”

I was tired of explaining, so I let the museum displays do the work by showing the story of this world’s god and the legendary ancestor.

The Demigod, who was at first believed to be God, originally brought prosperity. But at some point, it began trying to wipe out humanity. Desperate, humans entrusted their last hope to a hero. The hero couldn’t defeat the Demigod, but managed to seal it at the cost of their life.

Whenever humans began to prosper again, the Demigod revived and hunted them. Humanity sealed it again, repeated endlessly.

But then came a time when no hero was born, yet the seal still broke. And that was when the reincarnator appeared. The reincarnator, at first, was a magically inept student. Someone who could use many attributes, but all with weak output when compared to others.

Still, through relentless study, he surpassed all others in magic, became a renowned magician, gathered trusted companions, and finally defeated the Demigod. He later revealed that his magic was different and freely spoke of its essence.

He shared its principles freely, and that magic became the basis of modern magic. Thus, revered as its founder, he was called the Legendary Ancestor. And as such, this museum was built to summarize his history.

“So this history isn’t exactly accurate, right?” Fumitsuki asked.
“That’s true. But it’s not entirely wrong either.”
“I think I understand. This god, or Demigod, was never actually sealed at all.”
“Correct. With the old magic, defeating it was impossible.”
“They used the Demigod as a conduit to access the core of the magic’s power, right?”
“Yes, mana, ley lines, foundational world energy, that sort of thing. By channeling it through a Demigod, people couldn’t overuse it. A safeguard in a way.”

If the Demigod was an existence that could endlessly drain the world’s energy, then the idea was to control the amount they could use on their side first. The idea itself wasn’t a bad one, and if it had gone well, it probably could have allowed the world to live out its full lifespan.

Choosing a Demigod, rather than a spirit or something of that sort, for the role was also a strong point. And thinking of the worst-case scenario, they even left behind a safety net… or rather, if things didn’t go well, they had arranged it so the world’s purpose would shift in a direction other than simply letting it reach the end of its lifespan.

And the Demigod attacking people at first was simply a form of culling. Even if it controlled the world’s energy source, the infinite extraction placed a huge burden on the Demigod. So it culled them. It would only stop culling when a hero was born. After fighting the hero, it retreated somewhere humans couldn’t reach. That was mistaken for being sealed.

“But eventually the Demigod went out of control, so the reincarnator was sent to stop it.”
“Well, after so many cycles of culling, I suppose it warped.”
“And the reincarnator’s magic was untainted by the Demigod, right? It should’ve been weaker than the Demigod’s magic, so how could they win?”
“A complete surprise attack. The Demigod thought the reincarnator couldn’t use magic. So the reincarnator hit them with a spell strong enough to kill the Demigod in one hit while its guard was down. That whole sequence, from Demigod defeat to the present, was all according to the world-creator god’s plan.”

The reincarnator was considered weak not only because they could use the magic that relied on the Demigod, but also because they didn’t know how to use their own magic to begin with.

What overturned all that wasn’t just talent, but the training from early childhood brought about by reincarnation. Apparently, the god taught them the training method. The god probably taught it because they also wanted the Demigod defeated.

“Anyway, it’s about time.”
“Yes. The barrier is going to collapse.”

Lullus remarked further. When we left the museum and looked up at the sky, a crack had appeared in the sky, or rather, the barrier. Because we were staring upward, others followed our gaze and screamed. Hearing those screams brought more attention, and when people noticed the abnormality in the barrier, they each reacted in their own way. Most of those reactions were screams, then angry shouts. The thing that had protected them all this time was disappearing, and they had nowhere to put the emotions stirred up by this impossible situation.

A small number of people were resigned. They must have predicted this would happen sooner or later. Well, considering what was outside the barrier, it was an easy conclusion to reach.

Unrelated to the panic below, we casually climbed a tall building and watched the barrier collapse. It shattered with a crisp crack, like glass, but its fragments vanished into the air without raining down on anyone. The first visitor to this town, stripped of its protection, was destruction. Buildings collapsing, vehicles falling from the sky. Anything that had been flying was now pulled down by gravity. Structures that lost their balance crumbled.

We had foreseen that, so we stood atop a building that at least had decent construction. So we took no damage. Even if it collapsed, it wouldn’t have hurt us anyway.

Next, the ground began to wither. The environment outside the barrier seeped in, eating its way gradually from the edges toward the center. Strange monsters entered the town, like someone had mixed dozens of plants and animals and poured the result into a worm-shaped mold.

People ran in all directions, their feet sinking into sand, and were crushed and killed by the monsters.

“If there hadn’t been a reincarnator, what would have become of this world?”
“At the very least, it wouldn’t have ended like this.”
“So… does that mean what the reincarnator did was wrong?”
“It’s like choosing between a world that collapses in a hundred years but stays peaceful until then, or one that survives ten thousand years but is under constant threat. That kind of question. Though for you, Fumitsuki, it would be a problem if you didn’t already know which one is the correct answer.”
“I serve the God of Endings, I know that much.”

(Yeah, that makes sense.)

I thought as the town finally sank into the sand.