A single question with all context removed.

Its meaning was likely asking whether the conclusion was correct after already completing all mental calculations.

Or perhaps the conclusion was already determined, and he was observing how his disciple would react.

“Yes, that’s correct. She’ll leave after a set time. Probably… to the Demonic Cult.”

“She’ll be connected to that Heavenly Killing Star.”

“Um… yes, Master. I know you dislike Yeo Ha-ryoon, but.”

“…I understand, so say no more, Hee. I’ll handle it.”

If he said that, it was reassuring.

However, Master clearly has no intention whatsoever of improving his evaluation of Yeo Ha-ryoon.

Master’s long silver hair flowed down.

“Yes. You were a child who wanted to save people. Perhaps that person is necessary to prevent future calamities. Leave the rest to your master and go to the Imperial Palace’s Secret Archives.”

“Thank you, Master.”

“But rest for a few days before going. You look tired.”

“Ah, I’m perfectly fine as you can see.”

At those words, Master frowned on one side of his forehead.

“Not your body, but your mind. You haven’t forgotten that fatigue blocks thought and slows the flow of thinking, have you, Hee?”

His mouth was stopped by Master’s sound reasoning.

Zhuge Rin, displeased with his disciple, continued:

“I sent you for recuperation, but it seems you got involved in all sorts of trouble. I resent His Majesty. As always, royalty has never kept their word.”

“Master, that was something I had to do.”

“Yes. Considering the future, it was something you had to do. I know that too.”

As if looking at his disciple’s eyes gave him a headache, Master pressed his temples firmly.

“Anyway, tell me more details. What I know from information and what I hear directly from you will be different.”

“Hahaha. Master, I… brought snacks from Wannong! I sealed them tightly so they wouldn’t spoil and kept them with cold qi!”

“Good. Take them out.”

Jin Cheonhee took out Wannong specialties and placed them before Master, then shared various stories.

Stories about learning sorcery, about the Third Prince and the endemic parasites, about the Life Straw—that is, the Water Purification Tube—which Master found particularly interesting.

“Activated carbon… seems quite useful.”

Though used as a kind of filter when making the water purification tube, activated carbon itself had many uses.

Materials with holes throughout their surface and interior, like basalt, are called porous materials.

The basic principle is that this porous material, activated carbon, absorbs and removes contaminants.

Not only for purifying contaminated water, but also as a material for making gas masks.

It’s also effective for deodorizing and dehumidifying.

“We could use activated carbon to purify drinking water in the White Dragon Medical Pavilion, nearby villages, and the Martial Training City.”

“To do that, we’d need to overhaul the water facilities first, which would require a lot of budget and time.”

“In the past, we couldn’t have even dreamed of this.”

Activated carbon is used in modern water purification processes too.

Of course, that process is on a completely different level from the simple purification Jin Cheonhee created.

Water that has already gone through purification is treated with ozone to sterilize and remove bacteria and carcinogenic substances.

Then, remaining fine residues are removed through activated carbon.

‘Well, conversely, the water quality in modern Earth and this world are on different levels.’

Steam engines haven’t even appeared yet.

A world where buying water for money is unimaginable.

Just tweaking the basics a bit could make things much more comfortable.

‘But the unit cost is expensive…’

There’s no mass production system—a benefit of steam engines—so everything costs money.

‘For now, let’s not do anything grand, just separate the water sources to prevent contamination and install some basic filtration as a test.’

He tapped his head and began drafting a basic design.

“Hee-ah.”

“Yes…?”

“Stop working.”

“…Yes.”

At Master’s words, the blue light in his eyes returned to its original color.

Zhuge Rin frowned.

“Why does your thinking always jump to work?”

“I’m sorry…”

“Didn’t I tell you to rest now that you’ve returned? Is your master not welcome?”

Ugh, to say it like that.

Zhuge Rin showed a slightly sad expression.

Jin Cheonhee’s heart softened at those words.

“Um… Master is right.”

“Tell me about other stories too.”

“I brought soil samples thinking they might help with the stalled antibiotic research.”

Dozens of small sealed bottles appeared.

“You maintained them with Five Elements True Qi.”

“Yes, yes. Because the bacteria mustn’t die.”

“It’s strange. Bacteria survive perfectly fine in extreme climates, but why do they keep dying in the laboratory…”

I know, right?

Professor Jin became sad.

“It’s because we haven’t paid enough respects to them. But I thought cultivation might be easier using sorcery.”

“Progress would certainly be several times faster.”

“Yes. And once this is completed, I want to move on to the next research.”

“Next research?”

Aspirin.

Willow bark is already widely used as a medicinal material in every pharmacy in this era.

There are records of its use in ancient Egypt, and records remain of Hippocrates using it.

In our country too, Dongeuibogam[1] mentions that rinsing the mouth with willow bark alleviates toothache.

The price is also relatively reasonable compared to other medicinal materials.

Therefore, antibiotics are immediately needed.

Compared to penicillin or streptomycin, this was relatively lower priority.

However, Jin Cheonhee wanted not just analgesic and anti-inflammatory effects, but different medicinal properties.

‘Well, that’s still far off.’

For now, resolving the streptomycin roadblock is the priority.

Flick!

“Ouch!”

Stars flashed. Master flicked his unworthy disciple’s forehead.

“Thinking about work again.”

“Ugh… Master.”

“The Profound Origin Heaven and Earth Divine Technique is convenient for this one thing. I can immediately tell when you’re thinking about work.”

“But…”

“If you don’t like it, why not try calculating without the Profound Origin Heaven and Earth Divine Technique? Your efficiency would drop significantly.”

‘Aaargh!’

Master was displeased with his unworthy disciple overworking again.

So finally, reluctantly, he threw out bait.

“I suppose you’re not curious about the letters from your siblings.”

“…!”

The disciple’s eyes widened.

They were the eyes of an older brother worried about his siblings.

‘Anyway, having such an upright character is also a problem…’

But it was the highest quality for a physician.

And thanks to that character, numerous people continue to maintain relationships with Jin Cheonhee.

“There’s a letter from Sama Hye too.”

“Ah! I was wondering if she read the medical books I sent well.”

“She passed the junior physician exam safely, and after completing her training at the warehouse, she’ll take the intermediate physician exam and come to the main mountain, so it would be better to see her then.”

Jin Cheonhee frowned at those words.

‘The intermediate physician exam is difficult…’

Jin Cheonhee’s substantial involvement begins with intermediate physicians.

“I’m worried they won’t go easy on her.”

“Do you think that child would give up on her dreams for something like that? You’re underestimating her too much.”

That’s true.

“There’s also a letter from Wang Gak-yeon. She’s accumulated quite a bit of reputation, apparently. It seems she’ll return to the White Dragon Medical Pavilion soon.”

“Wow… really?”

“Yes. Though I’m not sure what level of reputation she’ll be satisfied with.”

Jin Cheonhee received lots of letters and gifts from his friends and siblings.

His flushed cheeks showed how much he missed those connections.

Zhuge Rin clicked his tongue at his disciple’s appearance, but still thought it fortunate that at least for now, he could forget about work.

***

First, he read all the greeting letters from his siblings and wrote replies.

Surprisingly, Cheon Woo wrote the longest letter.

Sama Hyeon sent the most gifts.

Though the letters weren’t long and there were no gifts, Yeo Ha-ryoon sent them most frequently.

The happiest news was that Sama Hyeon and Sama Hye had reunited.

Jin Cheonhee read the letters sent by the siblings simultaneously.

‘Ah, Sama Hye is a bit upset.’

He’s her only brother.

She probably noticed long ago that he was hiding something, but wouldn’t have expected him to hide it for so long.

She had reason to feel hurt.

‘But their reunion means… the “house cleaning” is somewhat finished.’

Though it’s unclear what level of cleaning Sama Hyeon meant, he surely did more than enough to ensure his sister wouldn’t get hurt.

‘There must have been internal changes in the Golden Blood Chamber.’

The gifts Sama Hyeon sent all looked so expensive that it was somehow frightening to touch them.

‘First, decorations for the room and ornaments for the tip of a knife. Hmm… this ceramic is scarier because I don’t know its origin.’

There’s also silk that looks obviously rare.

This is scarier because its source isn’t written.

‘Just give me money instead! Tell them to put it in White Dragon Foundation’s sponsorship fund!’

But then it wouldn’t be a gift.

Next is Cheon Woo.

The letter contained detailed accounts of the Wudang Sect’s recent situation and Fist Emperor’s well-being.

Strangely, despite the lengthy text, there was no mention of himself, which was somewhat concerning.

‘Is he doing well?’

From the text alone, one might assume he’s dedicating himself to training at Wudang Sect… but that’s only because Cheon Woo wrote in that style.

Tap tap-

Jin Cheonhee tapped the table and fell into thought.

‘If it’s just hitting a wall in martial arts, such a change in mindset is possible.’

It’s a process of endlessly cutting oneself down.

There will naturally be moments when one doesn’t want to talk about oneself.

Conversely, he might not want to worry his brother.

‘Hmm…’

After pondering, Jin Cheonhee decided to send a gift.

One is gloves made of White Silkworm Silk. Though possibly slightly inferior to Heavenly Silkworm Silk, he successfully preserved some of its functions.

Starting and stopping the project, there was still some finishing work left, but he thought he could complete it while resting at the pavilion for a few days.

In his reply, he would say that while dedicating oneself to martial arts is good, health should be the priority.

‘And that if there are any difficulties, he can discuss them anytime.’

What could have happened to Cheon Woo?

Hopefully it’s nothing serious.

In an era without messengers or phones, these exchanged letters were all they had.

Ultimately, feelings with nowhere to go could only circle around.

‘Even if you hit a wall, I hope you can move forward.’

When they parted at the Dragon Phoenix Gathering, Cheon Woo seemed particularly thoughtful.

Cheonhee did what he could as an older brother.