Chapter 1: Separation with Science

Dragon Era 637

Clack, clack, clack—the crisp taps of a wooden mallet rang out.

「Hmm... maybe it’s a bit too big.」

I narrowed my eyes at the tenon sticking out of the timber and shaved it down with a file just a hair thinner. It was a method called a mortise-and-tenon joint: you shape the ends of the timbers into interlocking bumps and hollows so they fit together snugly.
Given what we’re using it for, I’d prefer not to use metal nails if I can help it.

「Is it done?」
「Yeah. This should do it... there.」

I slid an axle through the center of the ring of fitted timbers and nodded to Nina, who had called out from behind me.

「That took quite a while, didn’t it.」

Nina looked up at the sun already past its zenith and slipping downward and let out a lazy yawn.

「Then you didn’t have to watch me.」

When I shot back, she ignored it.
She probably thinks I’m liable to do something dangerous if she doesn’t keep an eye on me.
Given I’ve already hit my fingers with the mallet twice by mistake, I can’t really argue.

「And now, this...」

I returned to dragon form, hefted the timber assembly, and from outside slid the axle into a small hole I’d made in the hut wall. In short, it was a waterwheel.

Ever since farming took root in our Hiiro Village over a century ago, harvests have become quite stable, which is wonderful—but eating wheat as-is is no easy feat. The basics are to grind it into flour and make bread or noodles, and that milling is backbreaking work.

You turn a millstone with a steady grind, but even an hour of cranking only yields about a single kilogram of flour. Against the several thousands—tens of thousands—of kilograms we bring in each year, we’re nowhere near having enough hands.

Hence, the waterwheel. Let the current turn the wheel, use gears to change the direction of rotation, and spin the millstone. Devices that transform a motion found in nature into some other motion are collectively called prime movers. If my memory isn’t failing me, the waterwheel is the oldest prime mover in the world.

With this, you just feed wheat into the mill and it turns itself into flour—the idea is to slash the labor required.
I first mounted only the wheel to the watermill, and the size was a perfect fit. The flow hit the paddles and the waterwheel began to spin merrily...

And then it stopped dead.

「Huh?」
「Looks like it’s no good.」
「That’s odd...」

Enduring Nina’s chilly stare, I checked the wheel; the flow was certainly striking the paddles properly. Thinking something must be catching, I gave it a push by hand, and the wheel spun easily.

Yet the moment I let go, it stopped. Something about the motion was strange.

「It ran fine when I tried it with a small model...」
「Maybe it’s too heavy?」

Casting a doubtful look my way, Nina poked the wheel with a little tap. At that instant, the wheel suddenly spun up at a furious speed.

「W-what...!?」

Startled, Nina jerked back. At once, the surface of the water began bubbling.

「I’m ba-ack!」

Up she burst from the channel with a splash—a mermaid girl with a fishlike lower body.

Blue hair that gleamed slick with water, long slender arms, and a waist fin that flared like a dress. Her large green eyes brimmed with curiosity, yet where I remembered a childlike innocence there was now a trace of maturity.

「Rin! It’s been a while!」

Rin, the mermaid girl who had once been my student—and even served as a teacher herself.
It must be close to thirty years since she set off from our village.
Given she’s of a race that belongs in the sea and yet came ashore in the first place out of sheer wanderlust, it was only natural that this small village would eventually feel too cramped for her.

「Yeah, long time—!」

Rin threw both arms around Nina and me and gave a hearty tug.

「Hey, wait—!」

Before we could resist, three splashes went up.





「...Honestly. You never change, do you.」

She wrung her clothes tight and voiced her complaint, but she was happy, I could tell. Nina’s expression was gentle.

「Ahahaha, sorry, sorry—got carried away!」

She might look more grown-up now, but inside Rin hadn’t changed a bit.
For long-lived folk like us, so much slips away when we live among humans; seeing her the same after fifty years was a joy.

「So it was you messing with the waterwheel, huh. No wonder it was acting weird.」
「Waterwheel?」

At my words, Rin tilted her head to one side.

「See, that wooden ring I just mounted. You were the one who stopped it, right?」
「Nope, I didn’t do anything.」

Wide-eyed, Rin answered. She loved mischief, but she wasn’t the sort to lie or play dumb. She was probably telling the truth.

「Then why...?」

I looked over at the wheel still mounted in place. It kept repeating that odd cycle of spinning for a bit, then stopping. Which meant, after all, that there must be some mistake in my amateur handiwork.

「Sensei, what’s that thing for?」
「Oh, that? It’s supposed to be something that the water pushes to make it turn... that was the plan, anyway.」

Then it hit me—the expert on water was standing right in front of me.

「Rin, can you tell what’s wrong?」
「Mm, no idea.」

She shook her head without hesitation. Figures.
Stuff with mechanisms like this was more Sig’s forte than Rin’s, after all.

「Why does the ring turn just because you soak it in water?」

And as it turned out, she didn’t get the basics.

「See how the water runs along the channel? It hits the paddles here and makes the wheel turn.」
「Why?」

How I’ve missed it—Rin’s eternal “why?”
She isn’t bound by assumptions like “it’s just common sense” or “that’s how it should work.” Back when she attended school, I felt like I heard her ask it every day.

「Wouldn’t the water just avoid something like that?」
「No, it’s not like water has a will of its own...」

I started to deny it on reflex—and then caught myself.

「It does.」

To my incredulous look, Rin stated it as if it were obvious.

「By ‘will’ you mean wanting to do something a certain way, right? It exists. In water, in stones, in wind—just like in us.」

The girl’s words were brimming with conviction.
It wasn’t the sound of primitive faith; there was an intelligent ring to it, and it struck me hard.

If what she was saying was true—

In this world, science would fail to hold together at the root.

I was a man who devoted his entire life to researching the occult.
Which meant I wasn’t all that well-versed in science and technology.

But even if I was clumsy with the techniques themselves, I understood what science was.

Because to know what counts as mystery, the unknown, the occult, you must at the same time know what counts as science, as reason, as the known.

And the single most important thing in science is reproducibility.
If you set up precisely the same conditions and do the same thing, you get the same result—that is reproducibility.
Whether in engineering or chemistry, everything is built upon reproducibility.

Which is why, for example, how someone feels when told “I love you” is a question science cannot resolve. Even if you arrange an identical situation, what one feels is an issue inside the person’s heart.

You can gather a large sample and derive “how they feel” statistically, but that’s the limit. Conversely, it means science cannot truly sound a person’s heart.

So if what Rin said was true, it would be a colossal matter.
If water and wind and earth—everything that isn’t a living creature—have wills of their own and move freely according to those wills, then reproducibility simply doesn’t exist in this world.

Even with identical conditions, whether the waterwheel turns would depend on the water’s mood at that moment. It might spin while someone’s watching to startle them, but it would have no reason to bother moving such a thing when no one is looking.

It was hard to swallow. If that were true, it felt as if not just science but the world itself would fall apart.

「Watch.」

But when Rin temporarily dammed the channel, then poured bucketed water down the emptied groove, the wheel began to turn smoothly from just that. Come to think of it, the conditions had been the same when I tested the small model—I had poured the water myself to check.

「Why does it work like this...?」

By volume and force, human-poured water is obviously inferior. If you think in scientific terms, the diverted river water should turn the wheel better. Yet in reality, the exact opposite was happening.

「Because you’re pouring the water to make the waterwheel turn, Sensei.」
「Well, yes, that’s true.」

She took the bucket from my hands as I held my head and scooped up water from the river to pour into the groove.

「Avoid the waterwheel.」

The moment she said it, the wheel stopped dead.

「Hold on, that’s magic.」
「Uh-huh. It is.」

Rin is a mermaid adept at water-manipulating magic. Even without much in the way of incantation, she can control water—so I started to think, and then a possibility struck me.

「Wait. Could that be it?」

Once, I defined a magic spell like this:
Words with intent, mediated by meaning, exercised with will.

That in itself was surely not wrong.
But perhaps it carried more weight than I had realized.

I poured water from a bucket with the intention and will of turning the waterwheel.
If that’s why the wheel turned... then what Rin is saying is that this, too, is magic.

And that isn’t all it implies.
Lifting a bucket with your arms.
Stepping on earth to walk.

Eating, breathing—living itself.
Every single one of those casual motions we make—no,
the world itself is magic.