"Hey~ Taa-kun, long time no see! They actually let you use the Fahrenheit, huh?"

Hetty-san, who had been in a strategy meeting with Rebecca-san and the others nearby, walked over and shot Efta a grinning look.

She loves giving people nicknames. Efta usually tries to act all cool and dignified, but being called "Taa-kun" by his big sister—and having decided not to bring any subordinates with him—made it clear that maintaining the dignity of the main family branch was going to be an uphill battle...

Then again, Efta always did prefer acting solo.

But the 'Fahrenheit', huh? I bet the main store back at the capital has a 'Celsius' too.

"Give me a break, Neesan... When a message comes in like that, I don't exactly have a choice. This thing has terrible fuel efficiency, you know... And I only got the Fahrenheit because the second brother lent it to me immediately after I explained the situation."

If I recall, the second son of the Solo family was in charge of Marishela. The eldest son stayed at the main store in the Imperial Capital as the heir... I think. I didn't care enough to remember the details. Hetty-san was definitely older than at least the second son.

One cannot defy an older sister. It is a universal law of nature.

"Heh. I wonder if he's finally softened his head a bit during his training in Marishela."

"Well, everyone knows how terrifying you are, Nee-san—Gah!? Ow-ow-ow-ow!"

Hetty-san began grinding her knuckles into Efta's temple. They really were quite a close pair of siblings.

"Calling such a kind, gentle sister 'terrifying'... how heartless can you be?"

"Neesan, you..." Efta hesitated for a split second.

"What? Is there something you're finding hard to say?"

The name Dida came up unexpectedly. Well, I suppose it's only natural; he was their uncle, after all.

"I heard the news. Well, that man had bought enough resentment from all over to last a lifetime."

"Back at the main house, there was a huge uproar that you had finally done him in, Neesan."

Wait, what?!

"Oh? How strange. Wasn't the official story that he died because a magic tool he was messing with went out of control?"

"Officially, yes, that's how it was handled. But since Uncle died a suspicious death in Erishe of all places—where you happen to be—it's only natural that people would suspect your involvement."

"I'm innocent. Well, not that I care either way."

Hetty-san actually was innocent.

It's true she helped, but the ones who actually did the deed were Ion and me.

"...Well, as expected, there's no evidence. And Father doesn't seem to want to pick a fight with you over it, so the matter was dropped. But... Father was quite angry. He used Uncle Dida quite heavily as an accomplice in his schemes. You might want to be careful."

If the old man was angry, it meant he was certain someone had killed Dida, even if it wasn't Hetty-san. I didn't intend for the target of his wrath to fall on the innocent Hetty-san. I might need to keep the possibility of a direct conflict with the Solo family in my sights.

However, I hadn't expected Hetty-san to be the one under suspicion, especially since the alibi-work was supposed to be near-perfect. Then again, Hetty-san has serious martial power and is openly at odds with her family, so I guess it's "only natural".

"Efta-san. Is it true that Dida-san died?"

"It's true. He was found dead at an inn in a town neighboring Erishe."

"W-What...? That man had visited here several times. Wasn't there talk of him acting as a support official for Diana's Guidance? He hadn't actually done a single thing for us yet, though."

In fact, he only came to get in the way.

Since he officially claimed to be our "support", I'd only seen him twice or thrice.

"That was the plan, yes. Oh, Jirou-san, do you know anything? When was the last time you saw him?"

"The last time I saw him was during the Knight Order's parade. We met briefly for the first time in a while and exchanged greetings, but I haven't seen him since. Honestly, for a guy who claimed to be a support official, he never showed his face."

"He was a man who moved only for his own convenience. To be honest, I didn't think he could handle a support role properly either. I suppose I should apologize to you for that, Jirou-san."

He was useless.

He really was incredibly useless.

"So, what was the cause of death? Surely you don't actually think Hetty-san killed him?"

I asked in a tone of common-sense goodness.

"The cause appears to have been an explosion of a magic tool. I can't go into the details."

"An accident, then. My condolences."

Efta gave me a slightly suspicious look, but I ignored it.

A man who didn't matter died in a place that didn't matter. There was no evidence. It was none of my business.

"Taa-kun, we can talk more about Uncle Dida tonight. Let's get the business over with first."

Hetty-san forcefully changed the subject.

In any case, I had to stick to the "I know nothing" story, and it wasn't like Efta had a specific reason to doubt me. Even if I had killed him, there was zero benefit for me in doing so.

"Right, yes. Err, so I heard you have a 'Guidance' active, Jirou-san?"

"That's right. It's been active for quite a while now: 'Conduct a trade with a Purveyor.' Basically, I want to do business with you, Efta-san."

"I see. But... 100 Spirit Stones? Are you serious? No matter how you look at it..."

I had asked Efta to bring 100 Spirit Stones for this transaction. That's roughly 300 million yen in value. For a private trade, it's a massive sum.

"I'm as serious as can be. Even 100 stones is a bargain. Provided you can use what I'm offering correctly, of course. You did bring them, right?"

"I could hardly refuse after the way Neesan told me to bring them..."

He said the stones were loaded onto the airship. Carrying 100 Spirit Stones on your person would be way too heavy.

"Then shall we get straight to the negotiations? Wait a moment while I get things ready."

I set up the items I'd prepared for the trade on a massive table in the square.

"...By the way, is all this... preparation for the Hitotsuzuki?"

Efta asked, looking at the massive construction project underway in the square.

Earth was being dug up, sandbags were being piled high, and watchtowers were being erected. Dwarves, female knights, and golems were all working together. I'd hired quite a few laborers for this. Monsters spawned at a decent frequency, so we could do live testing every now and then. I was feeling pretty proud of the progress.

"Yeah, it looks like this is going to be a big Hitotsuzuki, so it's a rush job."

"You don't know the type of Hitotsuzuki yet, do you?"

"It's still in the 'possibility' stage, but I heard it might be a 'Globe-Trotter'—there, finished."

As I spoke, the assembly I was working on was completed.

"What is this? Are you trying to sell this for 100 Spirit Stones? It's certainly a design I've never seen before, but..."

"No, not this... it's the idea. Of course, this isn't all, but let's start with this."

I flipped the switch.

Upon the winding rails, the object began to move with a rhythmic plastic clatter. Around it went, one loop, then two.

The Plarail was running. A toy locomotive was chugging along.

What I was showing Efta was a Plarail—a plastic toy train set from my world. I'd bought the rails and the train as a set at a toy store. Since it was battery-powered, it worked perfectly over here.

In essence, what I was trying to sell him was the concept of the railway and the power source. I was planning to sell him the invention that could revolutionize the transportation industry: the steam engine.

Steam engines and locomotives. The things that need no explanation.

Back in my hometown, steam locomotives are still in service; I've seen them and ridden them. However, the smoke is an issue, so they're mostly used as tourist attractions with high ticket prices. The fuel is either coal or coke, so it's likely more expensive than electric trains. Efficiency is probably lower too.

But this world has clean energy: the "Fire Fruit," the same fuel used in Lucraella. We use it at my mansion too; it doesn't produce soot, has high thermal energy, and yet it's a "cheat" plant that can be grown normally.

I don't know if this world has fossil fuels, but for fuel purposes, Fire Fruits alone would be fine. In fact, there's no doubt that Fire Fruit cultivation will become a key industry from here on. They're grown quite heavily already, but a shortage is inevitable. I might even start growing them myself.

Efta stared silently—just stared—at the Plarail as it continued to go round and round. In this world, the concept of a train—a vehicle that runs on rails—doesn't exist, at least not at a practical level.

Originally, the concept of the railway was born in mines. Minecarts used to transport excavated ore. At first, even the rails were made of wood. Yet, in Lucraella, the greatest mining town in the country, nothing like that existed.

Without a word, I plucked the train up and gently set it back on the rails facing the opposite direction. The train began its silent circling again.

A small breath escaped Efta's lips. "Ohhh...!"

"It can carry people, and you can make freight trains. Just linking the three cities of the Capital, Marishela, and Erishe would bring incalculable economic benefits. And if you set up stations along the way... you understand, right?"

"...Did you come up with this, Jirou-san?"

Efta asked, his eyes never leaving the circling Plarail.

I answered smoothly.

"The idea, yes. Furthermore, I have the invention of the power source required to operate it. I'm looking to sell that to you as part of the package. This is something that only makes sense if sold to someone with a certain level of power."

"And for that, 100 Spirit Stones..."

"It's a bargain, isn't it?"

"...It is not cheap. I don't know if I have the authority to make a decision like this on my own..."

100 Spirit Stones are, roughly speaking, worth about 300 million yen.

If this were a deal involving a major corporation, that wouldn't be much, but it's certainly not the kind of sum typically involved in a contract with an individual like me.

However, this is a watershed moment. Not just for me or for Efta, but for this entire world.

In this world, where magic makes life reasonably convenient, there's no doubt that people have spent the last 1,000 years living idly under the protection of God without any major inventions. 1,000 years is a long time. In Japan, that's the span from the Heian period to the present. By all rights, this world should have reached a level of development comparable to Earth by now.

Of course, I understand that in a world with monsters and such, things don't progress that easily. I get it, but there isn't even a steam engine yet. Not in this world. They've continued to live in a stagnant game world with the same level of civilization it had a millennium ago.

I'm not saying that's necessarily a bad thing. Progress has many facets, and a guy like me shouldn't presume to judge what's "right". I even feel like the human experience here is more "correct" in an essential way than it is on Earth. This world, managed quite literally by a "God," is likely much kinder than Earth.

That's why I don't know what will happen if that balance is disrupted by even a single steam engine. It might turn into a Steampunk world of steam and magic, or it might just fail to take root and fade away. It could even trigger a larger war.

But that's for the people living in this world to decide.

"This train is just a model. I think the real thing should be much larger... maybe about as wide as two adults with their arms outstretched. It will be expensive, but technically, there shouldn't be any issues. I've made a sample of the rails as well."

I set a piece of rail down with a thud.

It was a piece of a used rail I had brought over as scrap iron for Oyakata. I explained that I'd cut it down to a manageable size. Since it was an actual rail used in Japan, it was the perfect sample. I explained how to lay sleepers, set the rails, and pack it with gravel. The materials would require research; there's no need to stick strictly to iron if an original material from this world could do the job.

"And here is the power source in question."

I set down a model of a Watt-style steam engine (purchased on Amazon) that I'd stayed up all night assembling. A so-called steam engine. I placed an alcohol lamp under the flask and began heating the water. As the water boiled, the engine began to spin.

Efta stared intently at the sight.

"This is just a prototype sample, but I have separate blueprints ready. You might face some struggle getting it to a practical stage, but this power source can be handled by anyone as long as they have water and fire, and it's incredibly strong. It won't even compare to the horses currently used for transport. Of course, it can be used for more than just mobility."

Steam engines have a few weaknesses, but this world can cover two of them. Fire Fruits are a clean energy source that produces no soot (I'm not sure about the exhaust gas components, but given how this world works, the chance of it emitting hazardous substances is zero), and a mage can produce water from nothing. Of course, if they can build an efficient condenser to turn steam back into water, they won't need much, but it won't be that perfect from the start.

If there are blueprints and a Vocation-holder in engineering who can understand them, a practical version might be built surprisingly quickly. The logic isn't that complicated, after all.

"Everyone will be able to travel from city to city at the same speed as that airship you flew in on. The efficiency of transporting goods won't even be in the same league. You could call it a social revolution. It won't just be for locomotives; it can be used to power ships, too."

Now that I'd revealed the secret this far, I absolutely had to get Efta to buy it. Plus, I had the personal ulterior motive that if a railway were established, it would be much easier to go sightseeing in the Capital or Marishela.

Well, with his scary sister standing right there—and above all, this being a trade ordained by "Guidance"—the chances of the deal falling through were low, even if there was some haggling.

"...I'll ask one more time: did you come up with this, Jiro-san?"

"That's right. It's a grand invention, isn't it?"

I answered with desperate confidence, puffing out my chest. I'm a Vocation-scammer, so it's fine. Sorry, Watt-san.

"Even if you pay 100 Spirit Stones here, you'll make that back in no time once the product is finished. Though, since this will likely create a huge gap between cities that have stations and those that don't, you should probably keep the fare high at first."

If there's no station, the town withers. If it's far from the main lines, it withers. Ultimately, if you're left out of the flow of people, you decline.

But that's just the providence of society; it's something you have to accept as a byproduct of convenience. Besides, the disparity in this world is already more than enough. It's too late for that.

"...I never imagined a business deal like this. To be honest, I wasn't expecting much. I was feeling quite uneasy, thinking I'd been called here just to be asked for money."

"Whoa, Efta-san, what kind of person have I become in your head?"

"Something like a woman-chasing swindler."

"Harsh!"

But he's mostly right.

The moment I started a female knight order, I became suspicious as hell.

And since his sister, Hetty-san, is a member, he might be secretly annoyed. Efta seems like he might have a bit of a sister complex, after all.

"Still, this is truly surprising. Generating power from water and fire... But are you sure it's okay to sell this to me?"

"I don't know any other rich people, and besides, the Guidance appeared. ...Oh, but I'll ask you to promise one thing: don't use it for evil."

If used for evil, it could be used for anything. I particularly don't want it used for war.

"Evil... I'll do my best, but I can't make a promise. This will be a massive project, and naturally, there's no guarantee it will stay limited to peaceful applications."

"You just need to make a profit with this steam engine, get recognized, and become the heir to the Solo family. If you're at the top, no one will be able to object."

"Wh... Whaaat?!"

I didn't know Efta's exact rank in the Solo family hierarchy. But generally, the family business passes to the kin, and he should be able to overcome two older brothers. The chance is definitely there.

"Ah, I like that. It would probably be better for the country if Tar-kun took over instead of those two idiots at the top. If you're up for it, I'll support you."

"E-Even Neesan...?"

"Right, let's go with that plan. It's more convenient for me if my acquaintance Efta succeeds as a great merchant. We're 'comrades met through Guidance,' aren't we? Hahaha."

"B-But... No, can I really do it...? It's true my brothers only do safe, unremarkable work...?"

Though bewildered, Efta didn't seem entirely opposed to the idea. He seems to have a decent amount of ambition.

Just because he's the third son doesn't mean he has to play the "little brother" role forever. If something is within reach, he might as well reach for it.

—Afterward, the negotiations with Efta were successfully concluded, and I obtained 101 Spirit Stones.

From here on out, what Efta does with the invention is up to him. I hope he does well.