On the evening of July 15, the <> was extended from Gidami to the border.

Of course, this was the result of Jin and his golems.

By the way, on this day, Jin D was replaced by Jin himself, who came to check the progress of the highway. So, Reiko was there to guard him closely.

"Jin-dono!　I didn't expect you to build such a wonderful road so quickly!"

Industry Minister Jinzuo Mihoyas followed the golems and observed their work.

"It was a wonderful cooperation. ......"

The Minister of Industry said that when he was younger, he once wanted to pursue a career in manufacturing.

However, he had no talent for magical engineering ......."

At this point, Jin suddenly wanted to try it out. There were two Magi Crystals in his pocket.

"Mihoyas-dono, may I have a word?"

What is it?

"Well, there is a kind of engineering magic called Trans-Info. You can learn how to do it at ......."

First Jin explained the use of <> to Jinzuo Mihoyasu, biting his lips to include it.

"......"

Finally, on one of the two <>, Jin transfers his know-how on the basics of magical engineering as an example.

"<>"

"Oh, oh!

Do you understand?

Yes, yes!

"Then, please try to transcribe the contents of this control core into this Magi Crystal.

Jin relaxed, saying, "I just want to see your aptitude, so it doesn't matter if you fail,

"......Okay, now!"

and at the same time, he activates <>.

"<>!

"......"

The transinfo was properly activated.

Jin confirmed that he has about level 2.

"You have a talent for engineering magic, don't you?

"Really?

Yes. You should be able to use it from beginner to intermediate level.

Oh!

Then, please transcribe the contents of the Magi Crystal here onto yourself.

Having been so carefully instructed, Jinzuo Mihoyasu used without hesitation.

"Oh, what is this?

"...... It is the basics of magical engineering. Please review it carefully when you have time."

Jinzuo Mihoyasu was very excited to experience a part of the Horaijima-style magical engineering elite education method.

"Oh, oh, oh!　Jin-dono, no, master, thank you!"

"No, please continue as before."

Jin is a little taken aback when he is suddenly called "master.

* * * * * *

"...... By the way. By the way, this is the land around here..."

Jin spoke to Jinzuo Mihoyasu, who had regained his composure.

"Yes. Unlike the land up to this point, this area is completely incapable of growing crops.

The soil hardens when it contains water and turns to ash when it dries.

"That's why the eastern border is just up ahead."

Jin imagined that it was a decision made because it would not make sense to claim a barren land.

"But ...... umm ......."

Jin was concerned about the condition of the <>.

However, since he had no expertise in this area, he decided to just take a sample.

He formed a rock he found around there into a suitable container and filled it with soil.

"Reiko, load them into the hurricane."

"Yes, father. ...... Hope!"

Yes, ma'am.

Reiko, not wanting to leave Jin's side even for a moment, called Hope and handed her a soil sample.

Jin then said,

"Well then, Mister Mihoyasu, shall we go home?

but she refused and turned the Hurricane to the north a little.

Then he checks the mountain below.

"Hmm, I knew it. ......"

"Jin-dono, is that mountain something?"

No, it used to be a volcano.

A volcano?

There are no active volcanoes in Arus at this time.

Horai Island barely corresponds to it, but its existence was unknown except to Jin's friends.

"If it is a volcano, the soil at the foot of it is volcanic ash soil or ......"

Jin had heard that the soil was not suitable for growing crops, and he had been wondering if that was the case.

And then he wondered further.

"If it works well, I think it can be at least plastered with concrete ...... or not."

Jin hoped that he could make the concrete he had heard a little about ...... used in ancient Rome, which is said to have been made by mixing volcanic ash.

The durability of this concrete is outstanding, as evidenced by the fact that the Colosseum has survived to the present day.

However, Jin's knowledge is based on what he has heard, and he is not sure if he can reproduce it immediately.

Therefore, he intends to obtain samples and conduct experiments on Horai Island.

And <>.

This is a mixture of lime (calcium hydroxide), glue, and hemp (fibrous material), kneaded with water.

The calcium hydroxide absorbs carbon dioxide from the air and slowly hardens into calcium carbonate.

In Japan, where limestone is abundant, this type of plaster was often used for walls in Japanese architecture.

Some people believe that the word "plaster" is a corruption of "sessekai".

* * * * *

After Jin sent Minister of Industry Jinzuo Mihoyas to the capital city of Kuonare by <>, he returned to Horai Island once more via the eastern outskirts of the road, under the pretense of bringing back the golem.

"That's what ...... means."

Jin consulted Saki, who was on Horai Island.

"I see. So you want me to find out if I can use this volcanic ash soil to make building materials, is that it?"

"That's right. I know you're busy, but could you do it for me?

"Of course. Of course. How could I not do something as interesting as this?

Saki smiled and accepted the offer.

"Speaking of busy, you're busy too, aren't you, Jin?

"Well, yes. But with the old man and Makina around, it's still good.

"Well, let's try not to overwork each other, shall we?

"Yeah, I guess so."

Jin and Saki went to their respective workshops to fulfill their roles.