"It seems to be in the style of the Western Continent. It will cost a lot since we need to hire special workers, but it should work out somehow. Or I could make it myself."
"Yourself? The glass window?"
Jin Cheonhee looked at Yoo Ho with a questioning gaze.
The blueprint Jin Cheonhee had drawn required a large glass wall on one side of the house.
The rectangular glass would greatly enhance the lighting.
"This guy is really suspicious. No, never mind. Isn't vitamin D more important than that anyway?"
What Jin Cheonhee had designed was a triple-glazed window, without any opening or closing function.
It's more of a glass wall than a window.
Naturally, curtains were also designed for convenience.
A separate window for ventilation was also drawn in, and it was glass too.
With this, it seemed like he had at least some experience in architecture.
Could Yoo Ho really make all of these?
Yoo Ho rubbed his chin with his fingers and said, "If it was nonsense, I was going to give you a scolding, but this is beyond imagination. And it seems like it will definitely be effective. Whether it works or not, it's worth a try."
He confessed his misjudgment honestly.
It meant that he was starting to trust Jin Cheonhee.
Jin Cheonhee felt a bit happy.
"Of course, the sooner the better, right?"
"Considering the master's condition, of course."
"Good. Let's make the stove and the glass window within a day. For the underfloor heating, we'll have to call in a craftsman and start from the construction stage again."
He rubbed his chin, lost in thought, and then added, "If we move the master's quarters to another place, it will require additional work, but... we should make sure it doesn't take more than ten days."
"Great! With this, we can greatly alleviate the master's condition."
Ondol.
It's something that anyone who's read martial arts novels, especially fusion martial arts novels, would have looked up on the internet at least once.
It's not for nothing that the protagonist makes an ondol when they cross over to another world.
"Ah, I praise myself for watching that documentary to the end!"
Even if the design could somehow be done, making it required an expert.
Suddenly, Jin Cheonhee realized something strange in Yoo Ho's words.
"Wait a minute, you said you'd make the stove and the glass window in one day?"
"Yes, is there a problem?"
Yoo Ho looked at Jin Cheonhee as if asking why he was questioning the obvious.
"Come to think of it, this guy was learning some martial arts too. If he says it's possible, then it must be possible. But how?"
In the end, he couldn't hold back his curiosity and asked, "How?"
"Hahaha, do you think you're the only one with secrets, young master?"
"Ugh."
He hit the nail on the head.
Yoo Ho said, "My secret might not be much compared to yours, young master. But still, since you gave me a big surprise this time..."
"Are you going to teach me?"
"No. I'm petty, so I have to keep you curious like this."
He laughed playfully.
At first, Jin Cheonhee thought he was a scary and unpredictable guy, but now he saw this side of him too.
Yoo Ho said, "If it works out, I'll install it in your room too, young master. This is your achievement, after all."
In his voice, which pretended to be indifferent, there was quite a deep sense of gratitude.
The next day.
When he got up at dawn and went out, Yoo Ho was removing the old wooden window and installing a glass door.
"He really made it. How did he make that so quickly? It's been less than ten hours, time-wise. It's not like he has modern tools or equipment."
A thick question mark appeared on Jin Cheonhee's face.
Still, he decided to let it go for now.
The important thing was that the glass window was installed!
Moreover, right next to it, a new house was being built.
Seeing that they were laying the ondol first, it was an incredibly fast execution.
"Calling in craftsmen and getting them to work right away in just one day. That's incredibly fast."
Although it was a slightly different form from what was on Earth, glass was still glass.
Moreover, it was a triple-glazed window, making it much more airtight than wood.
"Now that it's installed, the house looks much brighter, young master."
"Yes. A lot of sunlight will come in."
Before, you had to open the window to get sunlight.
Now, there was no need for that.
"In fact, I thought the glass window would be harder to make than the ondol, but he managed to do it so quickly."
It's not like glass is common in this world either.
Even the Unryong Escort Agency used wooden windows with paper attached.
In human history, glass windows became widely available much later.
"Well, many things are different from the real Earth."
Jin Cheonhee scratched his head.
Yoo Ho said, "Ah, the stove installation is also complete. The master is inside."
"Really?"
Jin Cheonhee hurried inside.
Inside, he felt a warm heat.
His master, Jegal Rin, was sitting leisurely on a long chair, reading a book.
The warm sunlight pouring in from the rather large glass window was shining down on the master.
It was a dazzling sight, as if it could be a movie scene.
"Even in winter, just closing the window and lighting the stove makes it this warm... And with the improved lighting from the glass window, we've gained a lot of time."
Jin Cheonhee felt good looking at the room that had completely changed from before.
Jegal Rin reading a book while sunbathing looked so peaceful.
"Oh, Hee, you're here."
Jegal Rin sensed Jin Cheonhee's presence and spoke.
When he called him by his nickname, Jin Cheonhee's face turned red.
Being called by such a name at this age was not easy to get used to.
"If my real parents were here, would it feel like this?"
Baekrin's Immortal, Jegal Rin, said to Jin Cheonhee, "Come in quickly. I can't tell you how wonderful it is to be able to close the window and use the stove. My body feels so warm. It's like being soaked in a hot spring."
"How is your body?"
"Until yesterday, I was coughing all day and my throat hurt, but now it's much better. I can't believe how good this stove is... Hee, I can tell right away that what you made is really amazing."
Jegal Rin urged him to sit next to him.
"Since I'm small, the chair looks big."
Jin Cheonhee's small body wriggled onto the chair.
Jegal Rin smiled bashfully, finding Jin Cheonhee adorable.
"Our Hee is so smart and cute. No one ever thought of installing glass windows to bring in sunlight and increase indoor temperature. The head of the Namgung family brags about his successor being so great, but they probably can't even compare to you."
"Ehehe!"
"And what about this stove? It's so much warmer than a fireplace or brazier. I wonder why I didn't know about this until now."
"No, the reason they didn't install glass windows is because glass is extremely expensive in this era, and they don't have the technology to make such large glass, master."
In the first place, he couldn't understand how that extra, Yoo Ho, managed to make a glass window in just one day.
"And when did he make the stove while making the glass window? Is he using alchemy or something?"
Jin Cheonhee secretly doubted Yoo Ho's identity.
Realistically, bringing such a glass window in one day was absolutely not an ordinary task.
"Yoo Ho... I'll have to look into it later. Although he has extraordinary loyalty to the master, something seems suspicious. But since the master is so happy, I'm happy too."
Jin Cheonhee hadn't known Jegal Rin for long.
But Jegal Rin was a person whose love for his disciple was beyond imagination.
Look at him now.
His doting words were enough to give him goosebumps.
"I only knew medicine all this time. I was a frog in a well. You've removed the scales from my eyes."
Unable to hold back at the doting words, Jin Cheonhee said, "Ah, master, please!"
"Why, what's wrong?"
The master tilted his head and then said to the servant attending him, "Ah, bring some sweets. Our Hee must be bored. He's still young, so he should eat a lot."
At the master's urging, the servant hurriedly ran to the kitchen.
Yoo Ho didn't follow Jin Cheonhee inside.
But he didn't leave either.
He was standing, listening carefully to the voices coming from inside the door.
And Yoo Ho sighed.
"From the first time he saw Jin Cheonhee, he cherished him, and now he's become a complete doting fool."
Who is Baekrin's Immortal? He's not only a peerless doctor but also the last successor of the Jegal family.
He's someone who rarely smiles personally, except for the business smile he uses when necessary.
Moreover, as his health deteriorated day by day, the medical pavilion was filled only with silence and a gloomy atmosphere.
But ever since he met Jin Cheonhee, there was no end to his laughter.
"This is why people raise children."
It's not just any child.
It's a child with many secrets.
As soon as the child arrived, he started changing the cold atmosphere of the medical pavilion.
For Yoo Ho, it was a small but significant change.
There was also a practical change.
Jegal Rin's complexion improved.
Jegal Rin, who quickly lost body heat due to the Nine Yin Absolute Pulse, needed the heat in that sealed house for life extension.
The glass window.
And the bronze stove, designed to vent smoke without leaking.
These two alone would significantly support Jegal Rin's health.
How much more effective would it be when combined with the underfloor heating method currently under construction?
It was something extremely valuable to Yoo Ho.
"It wasn't just empty words. But having such knowledge is suspicious. The master says he doesn't care since he doesn't have much time left anyway..."
Yoo Ho's expression, lost in thought, turned frightening.
"Jin Cheonhee. If you truly save the master's life, I will give you anything. Even this life."
A chilling aura that no one could notice seeped through his narrow eyes.
Then, suddenly, he relaxed his expression.
Inside, he could hear Jegal Rin's laughter.
The venom in Yoo Ho's eyes quietly disappeared.
"It's been years since the master laughed..."
A smile appeared on Yoo Ho's lips.