While Jin and the others were chatting over a cup of tea in the cafeteria, the old man reported

"Oh, here he is. ...... Of course!　Let's hear it."

<

The old man projected a picture of the undersea scene on a monitor......<> in the dining room.

"Oh, this!"

.

The image is sent from one of the .

The reason why the deep sea, which should normally be dark, looks faintly bright is because the "Mere Old Man" is adjusting the image.

This is the depth which is called on the earth. (This is the area between 200 and 1000 meters deep.)

At this depth, there is a little sunlight, so it is not a dark world. However, we cannot see things clearly.

On Earth, there are about 750 species of deep-sea fish that swim in the sea.

"This area looks like a gently sloping continental shelf.

<

"Yes, I think so."

"Oh, there's something out there!"

Reinhardt shouted.

At that moment, something that looked like a deep-sea fish appeared on the screen.

Immediately, , who had received the instructions through the old man, approached the deep-sea fish, and the image became clearer.

The fish was elongated in shape and seemed to be twice or three times as long as the .

The head was probably covered with a number of thin, antenna-like, string-like organs.

"It looks like a sea slug."

Jin said in a whisper.

The longnose hawksbill is a large deep-sea fish with a distinctive appearance, and has become a topic of conversation on the rare occasions when it is washed up on the beach.

They drift in the middle of the ocean, far from the seafloor, and do not form schools.

They drift in the mid-ocean depths away from the sea bottom and do not form schools. ......, but here in Arus it seems to be different.

"Oh, there's a lot of them!"

"They're spectacular!"

Goose looks excitedly at the screen.

< were moving about.

One of them was nearly 10 meters long and seemed to be the leader of the group, swimming at the head of the pack.

They were swimming, but only slightly, and their speed was slower than that of human swimmers.

The first one we saw seemed to be a scouting fish, and it slowly joined the group.

"...... that was interesting."

"Yeah."

"Yeah."

After about half an hour, the fish that looked like a loggerhead disappeared from the screen.

"Hey, ......, what do you think about naming it the "Blue Gray"?"

A messenger, not a messenger. It was Jin who suggested it.

"Yeah, well, ......"

"That's good, isn't it?"

Goose and Reinhardt didn't object, and Erza and Hanna didn't say anything either, so it was decided that the fish was now called <>.

"So, what else is there to know about ......?"

<

It seems that the previous images were just a prologue.

"What?　What's that glow?"

<

Outcrop refers to a place where a part of a vein of ore appears on the surface of the earth, but Jin wonders if it is a term that can be used underwater as well. ......, Jin thinks about something relatively unimportant.

And Goose was curious about the magical crystals (magi crystals) that appeared on the ocean floor.

"Hmmm, that's strange ......."

"What?"

Goose responded to Jin's muttering.

"No, this Arus was an artificially modified planet, wasn't it?

"Yes, it was."

"The core is made of molecularly compressed superheavy matter, and the gravity is the same as that of Hale."

Yes.

"So it's strange that it has all these veins and volcanoes?"

Jin wondered now if the crust was not more stable.

"There were even hot springs in the village of Kaina. ......

Jin's line was, "I was wondering what you were going to say,

"I was wondering what you were going to say.

"Surely you don't know that now, do you?

"Well, that's understandable.

"But it's because you're my big sister that you have the same question, isn't it?

Everyone present reacted in the same way.

"What?"

Naturally, < Jin had no idea what that meant.

But he can guess.

"...... Oh, you mean that 400 years ago I knew the reason?"

"Yes, that's right."

"That's right, sweetie."

According to Elsa and Hannah, Jin had the same question 400 years ago, investigated it, and was convinced .......

"Well, ...... how do I explain it?"

"Well, I'm going to ...... ask you some questions, and you can tell me how to answer them, can't you?"

In short, you reduce the time of investigation to zero.

"Yeah, okay. Okay, I'll answer whatever I can."

Thus, Jin and his colleagues temporarily suspended the interim report of the old man and the underwater observation to have time to solve Jin's questions.

* * * * * * * * * *

"Okay. ...... First of all, the central core of this star is solid ......, right?"

"Yes, that's right."

"Yes, that's right. And what about volcanic explosions?

"Not since the dawn of time," he says.

Goose answers.

"Then why did Horai Island rise?　Couldn't magma have accumulated underground?"

Whenever Jin asks such questions, he does not give us direct answers, but sometimes guides us to the correct answers by guiding our thoughts.

"Geothermal heat rises with pressure, doesn't it?"

"...... I see, perhaps the crust is distorted by some kind of planetary deformation, and the pressure causes geothermal heat to rise?"

"Yes, that's how I interpreted it."

In this way, Jin confirmed the facts about the volcanoes on the planet Ars.