It was October 14, the day of the mock battle against <>.

This time, both Jin and Marikka visited the Agate base with their <>.

First of all, they contacted <>.

This was done without any problem.

<, do you read me? >>

<>

<>>

<

Since it was Agate base that won last time, it has the right to determine the area of the battle.

Then, let's use the same sea area as last time.

.

And that is the way it will be.

The start time is the usual time ...... about 3 hours from now.

<

* * * * * * * * * * * *

Now, at the Agate base.

"Yes, sir. Oh, please call them <>."

>. ......<> asks you to specify the combat zone>>

"...... Hmmm, same as before, right?"

"Yes, it is. ......<>,please reply that we should keep it the same as last time."

.

After such an exchange, Jin D. and Marikka D. decided to relax in the <.

"Well, the war will start in about three hours. All we can do now is watch.

"Yes, Master Jin."

Both of us are , so there is never a dull moment waiting.

They wait patiently for the time to come.

* * * * *

"Now all we have to do is wait..."

"Three hours, ...... is a long time."

In the dining hall of the research institute on Horai Island, the "Jin Family" was all waiting for the mock battle to begin.

"Kuhu, maybe I can understand how the old <> felt a little bit."

"I guess so."

Saki said, and Goose chimed in.

However, the <> only wants to confirm the outcome, not to enjoy the battle itself.

They just want to see with their own eyes the moment when the series of disturbances comes to an end.

"By the way, I had a suspicion..."

Bina spoke up as she sipped her tea.

"At <> or at >, we can see the images of the battle area, can't we? Do you have a magic tool like a <>?"

"No, no."

Jin answered.

"You have a choice of <>, don't you?　In other words, some of the sea areas are equipped with <>.

It could be the seafloor in the vicinity, or it could be something like a drifting underwater buoy.

Jin explained that the images sent from these buoys are processed and displayed on the screen.

"I think the image processing capability is amazing," Jin said.

Jin said.

The technology to project images on the screen in near real time from many different angles and from an unspecified number of people.

I must say that this is indeed the work of the , a man who has pursued entertainment to its very core.

"Ah, so that's how it is. But how have you managed to keep it up until now? ......"

"Well. Well, I guess... not the ones embedded in the seabed or rocks, but the floating buoys. ......"

Jin imagined that they might have had a good number of them, or had production facilities.

"No, no."

seems to explain.

"There is no doubt that there are embedded in the seafloor or in large rocks. But I don't think they are using floating buoys or anything like that.

"Then how?"

Jin wondered why they could only shoot images looking up from below. And so did the other members.

"That's a fair question. That's why we use a reflector.

"A reflector, is it? ......"

"Yes. But not a material one. We are using magic to create a mirror in the water.

"How?"

Simply put, we are using .

"Total reflection: ......"

Total reflection is described as <>.

For example, suppose we look up at the surface of the water from the water, which is a medium with a large refractive index.

Outside the surface of the water is air, which is a medium with a <>. If the angle of looking up is less than a certain value, we cannot see above the water surface.

In the case of water and air, the angle is approximately 48.6 degrees, which is called the <>.

"If you create a bubble of air or a vacuum in the water, you can create a totally reflective mirror by adjusting the angle of the interface."

"So that's the principle. ......"

Incidentally, <>, the reverse is not likely to happen.

In other words, it is almost impossible to create a totally reflective interface in air, a medium with a small refractive index.

The refractive index of air is 1.000293 (depending on the temperature) and that of vacuum is 1.000293. This is too small a difference in refractive index to be of practical use.

Therefore, it could not be applied to the reflector of the < that Jin and his group were considering the other day.

"As expected of the ."

It had never occurred to Jin that they were using a , so to speak, made in such a way.

It is not just a bubble, but a boundary that does not change its position. This makes it perfect for observation.

Since it has no substance, it cannot be destroyed.

The only drawback, Jin imagined, would be that it would be too dark due to its small size, but that could be overcome by amplifying it.

"I understand now."

Bina seemed to agree.

"Jin, if you win, have you decided what you are going to do afterwards?"

This is Reinhardt.

"I have decided."

Jin, perhaps a bit irreverently, but he had done everything he could to win.

"First, I'll send Marikka's golem and the team to secure the area, and then I'll go with Marikka to the east base at Gigosald.

"I see, so we'll be safe first."

"Of course, we'll bring barriers and transporters.

Jin answered that he would take all possible safety precautions.

"That's good."

Reinhardt agreed, and the other members of the were not displeased.

All that remains is to win this mock battle.

The time was gradually approaching.