Jin Cheonhee bought long bamboo tube-like pottery from the market and used them to design and create something.

“What are you making?”

Seeing him holding those long pottery pieces and doing something with them, His Imperial Highness Eun seemed curious.

What Jin Cheonhee was doing was simple.

He put cotton inside, then layered it with plant-based fabric commonly used in the region.

Then he made charcoal from coconut shells and burned it.

He ground it into fine powder repeatedly.

Then he naturally dried it in a sunny spot.

He found fruits similar to lemons in this region, extracted their juice, and mixed it in.

Then he fermented it again, applied heat again…

It looked like madness.

“I’m making activated carbon.”

“Activated carbon?”

“Hmm… it’s a kind of filtration purifier… I mean, a filter.”

“A filtration purifier… Just from the words, it sounds like a tool to make water clean… is that right?”

“You’re so perceptive. That’s exactly right.”

He put activated carbon in the long pottery tube, covered it with fiber and cotton, then added more activated carbon, followed by mineral stones.

He was layering various materials in the long tube like geological strata.

“But will that actually purify water?”

Would he understand if Jin Cheonhee said he was making a ‘Life Straw’?

What Jin Cheonhee was creating was appropriate technology.

That is, technology that isn’t expensive but is essential and can be used even in developing countries.

He wanted to create such appropriate technology items here in the Central Plains.

Life Straw.

When drinking contaminated water in Africa, putting this straw to your lips naturally filters out parasites and bacteria.

The filters inside act as a shield.

When this was first introduced, it wasn’t difficult to make, was very affordable by developed country standards, and extremely simple to use.

It received the highest praise as appropriate technology.

The problem was that it was ‘affordable by developed country standards.’

By African standards, it was murderously expensive.

So while it could be considered a failure as appropriate technology there…

Here, he judged that conditions were sufficient for its use and immediately began production.

However, since he didn’t know the golden ratio of cotton and fabric layer thickness and activated carbon quantity, he was experimenting with several samples.

Once this is completed, it’ll be much more convenient for caravan guards.

In the desert, water is scarce.

Since there’s no firewood to make a fire, camels must carry everything from the start.

But deserts don’t flow as desired.

Today might be good weather, but tomorrow you might lose your way in a sandstorm.

If bandits appear, you must risk your life and belongings whether you win or lose.

At such times, the only water source is an oasis.

Water contaminated with bacteria and parasites.

Of course, Wannong’s wells are also contaminated, but being water sources, they’re strictly managed by government offices and can’t be compared to oases.

The difficulty of finding wood to boil water is also incomparable.

Judging from caravan guards’ income, they had enough spare money to purchase these Life Straws, and the materials weren’t difficult to find in the Central Plains.

When a single sip of water can save a life, there’s no reason not to make it.

Jin Cheonhee explained to His Imperial Highness Eun in the most understandable way possible.

His Imperial Highness Eun rubbed his chin thoughtfully, then said:

“If what you say is possible, it would help not only caravan guards crossing deserts, but also numerous military officials crossing rough terrain.”

“Yes. At least we can prepare for local endemic diseases caused by contaminated water. Ah, of course it’s not a cure-all.”

“That alone sounds impressive… but whether it can be made as easily as you say is the question.”

It didn’t require advanced metallurgical technology.

The difficulty level of making activated carbon was within the capabilities of charcoal makers.

If successful, it could save many lives.

Eradicating all parasites is impossible anyway.

In an era without plumbing systems, there’s a limit to purification no matter how thorough.

However, it could prevent many situations like the Third Prince’s case caused by local parasites.

I wish they’d be careful about animal excrement too.

Since they’re zoonotic parasites, horse dung should also be avoided.

It would be good if soap distribution could be introduced together.

For now, testing the Life Straw was the priority.

His Imperial Highness Eun said:

“Good. I’ll give you five days. If you succeed within five days, I’ll reward you.”

Oh, that sounds good!

***

After completing various samples, the moment for testing arrived.

The test method was simple. Just suck on it.

Hwanggu would evaluate the success.

Jin Cheonhee dipped the Life Straw into muddy water and instead of sucking with his mouth, gently drew water through it using his breathing technique.

Woof!

Though it looked clear to the naked eye, Hwanggu seemed to think differently.

“Hmm… alright. Let’s try number 2.”

He tried again.

Growl!

“Better than before? So the ratio of activated carbon is the issue.”

He kept repeating the process.

“I need to apply a layer of glaze inside the pottery… this…”

He tried several combinations of special glazes applied to the pottery and fired them multiple times. Eventually, His Imperial Highness Eun personally recruited an artisan to help Jin Cheonhee.

As they approached the final test…

His Imperial Highness Eun said he would send a person to conduct the experiment directly.

I could just use my breathing technique?

Well… I suppose it makes sense to test it as it would actually be used.

And then arrived the said artisan.

“Ah… hello, Imperial Inspector.”

A familiar face was approaching Jin Cheonhee respectfully.

“Ba… Battalion Commander Baek[1]?”

Judging by his clothes, he seemed to have been stripped of his Battalion Commander status, wearing ordinary soldier’s armor and carrying a standard-issue spear instead of his once-magnificent sword.

“Battalion Commander? How presumptuous of me. I have now been placed in a position befitting my station.”

So fast… is this kind of handling of affairs supposed to be this quick?

“But… you’re not exiled?”

Since things had come to this, he decided to ask directly.

“His Majesty said it would be a waste of taxes to exile me… so he confiscated my property and gave me a chance to atone for my crimes.”

Hmm, serving in the army wearing white in this remote region—it means they’ll drain his labor until death.

Both His Imperial Highness Eun and His Imperial Highness Geum who works with him dislike money leaving the national treasury like this.

If this guy were a high-ranking official, they would either annihilate his entire clan or execute him to root out the problem.

But it would be a waste to send such a small fry on a forced package tour called exile.

They’d consider beheading him, but even that seems like a waste of money.

It might be better to just behead him…

Since they said they were giving him a chance to atone for his crimes, they’ll probably torture him with false hope, then send him to a dangerous place at an appropriate time to die…

His Imperial Highness Eun isn’t merciful to criminals.

He’ll thoroughly use him as a disposable piece, then likely turn him into a ghost who never returns when the time comes.

And his first mission.

“Should I put this pottery tube in the muddy water and suck from the other end with my mouth?”

If the experiment failed, he would have a stomachache tomorrow, and by next year, parasites would be establishing kingdoms inside his body.

“Well…”

In a world without human rights, villains have even fewer rights.

Jin Cheonhee scratched his cheek and said:

“I’ve already tested it several times with my breathing technique, so it should be safe.”

“Yes, yes. Of course. I understand.”

Only then did the former Battalion Commander look relieved.

His Imperial Highness must have been manipulating him tremendously.

Jin Cheonhee felt a tiny bit sorry for him, but when he saw Hwanggu’s face, that feeling disappeared.

Right. You reap what you sow.

Jin Cheonhee decided to be thick-skinned about it.

At that moment, a voice rang out.

“Ah, you’re already conducting the practical experiment?”

The masked Imperial Highness Eun and the Third Prince were walking leisurely together.

Luxurious clothes and an unusual dignity. Although their faces were covered by masks, their presence was intimidating.

When the former Battalion Commander tried to prostrate himself, His Imperial Highness Eun said:

“Ah, I’m just an ordinary caravan leader. Don’t mind me and continue what you were doing. This person is just my friend.”

Hearing the words “caravan leader,” the former Battalion Commander sighed and said:

“Ah, that’s a relief. As a mere soldier carrying out His Majesty’s mission, I cannot bow my head to just anyone.”

Oh wow, look at how arrogant he is.

This guy truly had a golden disposition from the start.

Even in this situation, he was clearly trying to get friendly with the caravan leader to gain some advantage.

Seeing that behavior, the sympathy that had briefly entered Jin Cheonhee’s heart flew away.

“Hoho, so you’re doing national work.”

As expected, His Imperial Highness Eun’s lips twisted gently beneath his mask.

Others might see it as a smile of approval, but to Jin Cheonhee’s eyes, it was the opposite.

It was like a lion sizing up a lamb for the kill, making his knees weak.

The former Battalion Commander, seemingly oblivious, stroked his beard.

“Ahem. It’s not such an important position.”

I don’t care anymore. Just hurry up, suck, and go home quickly.

A good adult can do nothing but pray for this bastard’s soul.

Get him to suck quickly, test quickly, and send him home quickly.

Perhaps lighting some incense for him about a week later is all that could be done.

“Let’s get on with it.”

“Ahem, Imperial Inspector, there’s no need to rush…”

Had he smelled money from the silk His Imperial Highness Eun was wearing? Why was his tongue getting so long?

“Just do it quickly.”

Under Jin Cheonhee’s silent pressure, the former Battalion Commander reluctantly squatted in front of the muddy water.

Then he slowly dipped the tube into the water and sucked.

His expression darkened, perhaps foreseeing a future of drinking muddy water. But that was only momentary.

“Oh?”

“Is it alright?”

At that moment, Hwanggu barked softly.

Woof!

Even wagging its tail—a clear “pass” signal.

The former Battalion Commander said:

“It’s a bit uncomfortable to suck, but it tastes like well water even though it’s muddy water.”

“Let me check your pulse right away.”

Jin Cheonhee placed his hand on the former Battalion Commander’s neck and attempted to examine his qi and pulse.

It certainly seems fine.

But it’s too early to completely let down his guard.

“Could you come back again after a day?”

“If the Imperial Inspector says so, I’d be happy to. Hehehe.”

He rubbed his hands eagerly.

“Um… could you just mention that I worked hard when it comes to extra compensation…”

So this is his true intention. He’s definitely not smart compared to his greed.

“I understand. I’ll definitely! Mention it.”

Jin Cheonhee glanced at His Imperial Highness Eun, then immediately continued speaking.

His Imperial Highness Eun smiled slightly, as if finding Jin Cheonhee amusing.