The Demon King’s Proclamation
On that day, all of Earth’s people came to know that there was something mysterious happening with their world.
Everyone other than those who had just been born or those who had already died looked towards the skies.
What they saw was another planet. 
Having blue oceans, green stretches of land, and white clouds, it was a planet that looked similar to Earth.
It was another world.
The satellites that should have been orbiting their planet all disappeared, along with other space stations, causing each country to fall into chaos. However, each one observed this new world and recognized the traces of intelligent life, contacting one another.
A certain hasty country set out reconnaissance aircraft… and confirmed that there truly was a world there.
The cause was unknown. Its very existence was unscientific and was a contradiction to all known laws of physics.
A planet had come in contact with their atmosphere. It had very scarce artificial lighting.
Another certain country judged those lands to be undeveloped and tried to send in an aircraft carrying people to occupy the land, but it failed.
The planet had allowed drones, but manned aircraft were refused. Those aircraft were blocked by the atmosphere, but managed to return home safely.
What was it? Everyone the world over discussed it.
Each country held conferences with their specialists, but the everyday internet users instantly guessed what this signified.
Even if they didn’t know anything else about it, it was definitely another world. 
Even through the use of commonly bought personal telescopes, the traces of intelligent life could be found on the planet. Rather, the intelligent lifeforms themselves could be seen.
Excitement swept across the world.
Three days later, it appeared.
What looked like a massive screen appeared in the skies in two thousand locations throughout the world.
A figure was in it wearing gold-embroidered black clothes, a gold mask, and a black mantle with horned headpieces on the shoulders.
“Greetings, those of Earth.”
With the voice of a young man, the messages mysteriously managed to accurately use all of the Earth’s languages.
“I am the one who rules this world’s greatest domain. I am Ars, the Demon King.”
That single statement held a great amount of information.
“Those of Earth, you still do not understand what is happening, do you? Before we continue, allow me to explain.”
It truly was information they wanted quite a lot.
“First of all, your world… the world you call Earth, exists in a universe that has a limit. Although explaining exactly what that limit is would be somewhat difficult, suffice it to say that that limit concerns the capacity of how many worlds may exist within it. We’ve arrived at one of those limits, so our two worlds have been connected.”
Ars put his elbows on the desk and crossed his hands in much the same way Shifaka often did.
“If we left things to continue on as is, our two worlds will collide into each other and disappear. There are several paths in order to deal with that, but we have already chosen the path that will be taken.”
With that, Ars paused, speaking slowly.
“We will destroy the Earth.”
It took a few minutes for what he said to sink in.
Ars waited in silence for that period of time. Around three minutes later, he began to speak again, but Earth had already been thrown into chaos by then.
It was natural. Someone suddenly appeared saying that they would destroy the world.
The world’s superpowers—the United States included—made official war preparation announcements.
“By the way, we are prepared to accept immigrants from Earth. However, there is a limit. Six hundred million people. That would be the ideal amount.”
Although the Demonlands’ bureaucrats desperately calculated the upper limit that could be accepted to be closer to one billion, there was no need for him to speak so honestly. Humans were a race that would multiply. To somewhat guarantee them a certain standard of living, the less of them there were, the better.
“We are willing to accept engineers and scientists along with their close relatives as priorities. However, we have no use for humans will unproductive abilities.”
He spoke coldly, very much like a true Demon King.
“Moreover, we refuse to accept the sick and elderly unless they hold unique skills.”
He spoke ruthlessly, saying that nuisances were unnecessary. This was also something very Demon King-like.
“You have five days, please use them wisely. At noon of the fifth day, we will send several messengers to the Japanese parliament building.”
Saying that much, Ars leaned back into his chair in a relaxed manner.
“Although it will not be possible to invade our world until then… you are free to try. It has been set such that any objects with a living signature will be temporarily rejected. In the case we are attacked, we will immediately consider it a declaration of war and eliminate the country responsible.”
If you want to give it a shot, go for it. That’s what Ars was saying. It was to cause countries that were quick to fire to have second thoughts.
“Well then. See you in five days. We look forward to meeting the leaders of your various countries in Japan.”
With that, the projections all disappeared.
“Aaah~, I was seriously nervous during that speech. I didn’t trip up anywhere right?”
Taking off his mask, Ars had cold sweat dripping down his forehead. He used his hands to wave air against his neck.
Their world’s various royal families and strong people were invited into a facility similar to a university’s lecture room. There were many people unable to make the trip due to the distance involved, but they too had been sent information through communications.
“Even so, what you said was pretty one-sided. There aren’t any God Dragon-like strengths on Earth?”
The youth that spoke up was Prince Sion of Lemdria. Although he was a genius when it came to strategy, he wasn’t able to overcome the demons’ overwhelming war potential in the previous war.
Accepting the water someone had brought to him, Ars gulped it all down and took a deep breath before answering Sion’s question.
“It’s alright. Although they have weapons strong enough to turn our world’s continents into wastelands… they do not have a weapon capable of destroying a planet.”
“That’s still something to worry about. Do we need to put up barriers to counter it then? By the way, you spoke of weapons, but what about Earth’s mages?”
“Well, if they have weapons that are that strong, wouldn’t the world’s magic be just as strong?”
“Oh. Oooh, oooooooh~”
Ars covered up his face in what looked like a face palm, reflecting on his thoughtlessness.
“Well, you know, Earth doesn’t have magic. At least to my knowledge, there isn’t even a single mage on Earth.”
Sion’s mouth stayed open. It probably really was something incomprehensible to those of this world as its civilization was developed with magic as its premise.
Magic was the basis for communication, farming, and even raising cattle. All magic tools used magic crystals—masses of mana—as their fuel. Moreover, cutting edge technology made use of magic cores.
“In other words, they only use magic crystals for maintaining their civilization? You should still need magic to make magic tools though…”
“Weeell… let me tell you a bit about Earth’s civilization, alright?”
He then explained the development and growth of science through ancient times, the middle ages, the early modern era, the industrial revolution, and the modern era. He explained the transition of what was used as fuel in as much detail as possible. 
Regarding the industrial revolution’s steam engine, Serge had been invited into the explanation to give more details on it.
This Demon King-sama had lived for more than a thousand years. He didn’t remember too many details from that era.
“In conclusion… their studies concerning mathematics far outstrip ours? Couldn’t we make use of that in our world?”
“It’s possible, but I think it is better to tread that path very, very carefully. Once you make machines through science, humans become unnecessary, leading to problems with masses of unemployed individuals.”
Unemployed people would flood the city, leading to the degradation of public order. Something similar was starting to occur in this world as well. War refugees displaced by the demons’ invasion were now on their way to return home, though.
Prince Sion grew quiet as he fell into contemplation.
After that, questions came one after another. Ars had Thor and the other reincarnators help out in answering their questions.
They were surprised that Gifts and Skills didn’t exist, but it might be fine to say that they did exist yet just weren’t quantified into numbers. It took mana to use identify-type skills to quantify them into numbers, after all.
“I see. The more I hear about their world, the less I understand it.”
Everyone in the surrounding group of people agreed with the person’s mutters. Ars should have spread some of the technology one thousand years ago as well as Thor another thousand years before that, but not much had remained. The only place it succeeded in seemed to be the Demonlands.
“Even so, it’s strange that the world that the Heroes are summoned from has no magic…”
“There are traces of its existence in the past… but now it is thought of as superstition.”
Even Ars was doubtful about that subject. Things like the qigong Ria had practiced in her previous life could only be seen as magic.
“For the time being, we’ll assume that Earth’s army will definitely attempt to attack. What we need to pay the most attention to out of their weapons are what are called missiles.”
Ars briefly explained to his audience about what would be assailing them soon enough.
“That nuclear explosion thing you mentioned, is its strength at the level of the forbidden fire magic?”
“Such power… only a huge city’s barrier might be able to defend against it.”
“Us demons are already prepared to handle that. Same with the God Dragons, or at least Ohma-sama will be giving us her cooperation.”
The assembly hall filled with noise, but as far as the world’s protectors, the God Dragons, were concerned, nuclear weaponry causing the amount of habitable land to diminish would be troubling.
Valis appeared to be concentrated on destroying Earth and Lanna was somewhat worn out from using her power to send the current era’s Hero to another world. As for Terrew, she would exercise her power the moment their own atmosphere was invaded.
The extended conference coming to an end, Ria gave Ars, who looked tired despite likely not being too tired, a cold gaze.
“No no, you saved me quite a lot there. As expected, those who’ve made it through to post-secondary schooling are different.”
Who he was conversing with was Serge. Ria herself wasn’t too useful.
“Even so… even if we can win, it looks like we’ll have our own deaths.”
Ria was concerned about it. Ever since she decided to fight for this world, she was thinking about how to lower the death count as much as possible.
“I don’t think there will be too much damage as long as it’s not declared an all-out war and America starts doing indiscriminate carpet-bombing, at least.”
“Well, that’ll depend on the negotiations with me and Nee-chan.
Yes, during these five days Ars gave them, it was decided that Ria and Serge were to go to Earth.
As an aside, Labyrinth was invited as well, but she withdrew into the labyrinth. It appeared that she didn’t really even want to meet her acquaintances from her previous life. Well, as an elf, she would have stuck out quite a lot on Earth though.
“So, are you prepared?”
“No problems here. We’ll be flying there soon.”
“In truth, I’ll be teleporting us there though.”
They would be using Serge’s teleportation magic as their means of transport. Although they could break through the barrier and fly their easily, they were concerned about retaliation coming from Earth.
Their destination was Japan. They’d already decided on what actions to take.
“Ria, Serge, please be careful.”
Carla spoke, an uneasy look on her face. Ria kissed her on her cheek.
“Don’t worry. If push comes to shove I can just transform into a Dragon and come back.”
Although Ria’s statement made Serge start to get a feeling that something might end up happening, he heard a voice come from nearby him.
It was Prince Sion, the one who had been speaking actively in the meeting.
By the way, between Sion, a prince, and Ria, an archduke, Ria was distinctly of a lower rank. An archduke wasn’t royalty, after all.
“You’re leaving already?”
“Yeah, right now even.”
“That so? If you can, could you try to get a hold of some of Earth’s weaponry? Nuclear weaponry in particular.”
Although his request surprised Ria somewhat, she smiled in the next instant and asked for his reason.
“They’re weapons you’ve said are strong enough to decide the outcomes of battles by themselves. Don’t you think that we should study them?”
The three who’d come from Earth looked at each other before looking over to Ars.
“Your Highness, those weapons have very sensitive matters keeping them held close to the chest, if you will.”
Leaving the explanation to Ars, the two looked back towards Carla.
“Alright then, we’re off.”
“I’ll buy you some souvenirs!”
Serge spoke in a light tone, but he quickly grew concentrated.
Unlike the short distance teleportation he could use offhandedly, this was a long range teleportation that would bring them all the way to Earth. It took him time to construct the formula.
Constructing the magic even while thinking about something as carefree as how he had to buy something for Chris as well, he finished, the two of them teleporting away.
- Umm… how could everyone see it!? Spheres! Return
- Note that they’re specifically using the term used for the genre/common trope. Not just “another planet”. Return
- Note that this line used various Japanese-defined eras that require much more historical Japanese knowledge than I have to translate properly. Because of that, I localized it somewhat. Return