Jin is making a magical tool that can be applied to the body.

"As long as the <> is efficient, it can be made smaller."

"...... Jin brother,<> shouldn't be generalized?"

Erza, who was watching from the side, said.

"Yes, indeed. Then, let's make the mass-produced ones with mana tank specifications.

"Yes, that's a good idea.

Thus, the first prototype was completed.

In appearance, it is a miniature flashlight that uses two AA batteries, not an LED.

"To make it easy to see the range of the effect, I made it so that the area illuminated by the red light would be <."

"Good idea."

I tried ...... on some stones, but it turns out that the area of effect is too wide to be suitable for small objects.

"Let's make the range adjustable," he said.

"Let's make the range adjustable," he said, and added a zoomable format.

"This time it will be better."

The red light illuminates a square meter of stone.

"When the toughening process is finished, the object glows red.

"It's easy to see."

"The thicker the object, the longer it takes. The thicker the object, the longer it takes, because the process gradually moves from the surface to the deeper parts of the object.

You need to keep shining the light during the process, but if you stop halfway through, only the surface or even the shallow part will be treated.

"Yeah, that's why it glows red when it's done."

"That's what I mean."

The stone is 10 cm thick and the process takes about 10 seconds.

"It could be faster, but then it would be harder to use when you only want to do the surface.

"Indeed."

At any rate, this completes the magic tool for applying <.

"If we make this into a mana tank, we can make it into a mass-produced product. ...... Wait?"

Brother Jin, what's wrong?

"No, I just thought that if I can cast a toughening spell, then I can also cancel the toughening spell.

Although he didn't have that kind of engineering magic, Jin had a hunch that it would be easy to make.

"And I think I can also make a magic tool that weakens the bonding force," he said. ...... This is not good."

"What?"

"I thought it would be easy to abuse. ...... So far, only those who have mastered engineering magic have been able to cast . But if this magic tool becomes widely used, anyone will be able to do it."

"Nope."

"But it also has the potential to make it easier to do the opposite of what you just said."

Jin said that with the magic tool made to this stage, it would be possible to create engineering magic that would have the opposite effect by analyzing it.

"In other words, a magic that weakens the molecular bonds and makes them fall apart."

"...... I certainly think it can be done."

At this point, the old man's voice came out.

"My Lord?　What do you mean, after all?"

"Is that so?"

"Indeed. Now I remember. ...... Jin's brother had the same idea when he was 43 years old and came to the same conclusion. ...... I didn't have the idea at that time, though."

"I didn't think so. ......"

Jin was somehow convinced that he would always be himself.

"...... then the <> magic tool is a dead end. ......Maybe Reiko knew about it, too?"

"Yes, father. I'm sorry."

Jin was strangely convinced that this was the reason why he had helped her without saying anything until now, while he usually made some kind of comment.

"I must have had a similar thought 400 years ago."

Jin was enjoying himself a little.

"But if that's the case, ......"

Jin tried to imagine what he would have done 400 years ago.

"Old man, did I ever create an engineering magic like ?"

<

"I knew it. ......"

< and makes it brittle.

The original use would be to demolish buildings or to dig up paved surfaces. .......

"It can be used to attack castles."

If used on walls and gates, it would be easy to break through.

"It would be ...... horrible if used on a golem."

A metal golem could be broken just by a human punching it.

"...... So, 400 years ago, I thought of a countermeasure for that, didn't I?"

Jin thought that he must have thought about it so that it would not be effective even if it was used by the Horai Islanders, and he was right.

"It must be a magic to be used after <> to <> the effect."

<

"And ......<> can't be nullified by magic to cancel <>, can it?"

"I see."

Jin doesn't dare to know the original achievement.

There was a time when he thought it would be better to know, but he decided not to.

However, <> if Jin is about to do something too wasteful, Rokun or Reiko is supposed to point it out to him.

Jin likes this situation very much, and it will continue for a while.

"In the end, it's the turn of the <."

He is capable of defending himself against most threats, and he will not be a party to any wrongdoing.

<, the hotel being built in the village of Toka will be safe and secure.

"The question is the price."

Jin thought for a moment.

"We could support them secretly ......."

Or, we could get support from the . Jin decides that the latter would be more plausible.

"Since you are offering us a place, we will give you some assistance, I guess."

The old man also agreed that it would be better that way.

"Good."

Jin took Reiko and went to the Nordic Federation by warp gate. They went to visit Theon.

"Welcome, Jin. So, what can I do for you today?"

"From the very beginning, you think I'm here to ask you a favor."

Oh, no?

"No, I'm not ...... different."

So Jin began to explain to Zion the reason for his visit.