The hole that Hinata discovered was in a rather secluded position, and it was obscured by an undersea rock. Pen @ fun @ pavilion wWw. ｂｉｑUｇE。 info can't find the hole from above. There is also a large amount of seabed rocks piled up in the surrounding area, causing serious shading.

This very complex terrain is naturally easy to overlook, and even echolocation can be disturbed by the complex rocky environment of the seabed. Therefore, it is very difficult to discover this underwater cave.

After discovering this suspected passage to the underground world, Hinata and others immediately launched an exploration and analysis of this cave.

After comparing the density of the water flow, the oxygen content, the temperature difference, and the already all-important amount of nanomaterials, Hinata determined that the cave did have a good chance of reaching the underworld.

There is a problem though, the diameter of this cave is a bit small. Bismarck's size is completely unpassable. Even the I-401 was barely able to enter. And whether it will get stuck in the middle of the cavern, no one can say for sure.

Originally, Yun Qi was still worried about how to appease this arrogant eldest lady Bismarck, if he didn't take her with him, in case she launched a saga, he insisted on staring at Klein's position and forcibly entering this cave. That's a problem. Yun Qi didn't want to be buried alive in the collapsed cave halfway!

As a result, Iona gave Yunqi a surprise. It seems that since the last incident, this little girl seems to have opened her mind. It's no longer the same as before, I don't care about anything, and I don't care about other people's feelings. Now Iona is starting to care about people.

When Iona offered to ask Bismarck to stay and help them guard the entrance, Bismarck, the tsundere housemaiden, immediately agreed. She agreed to Iona's request very clearly, but asked Iona to go with one of her split dolls. This curious otaku doesn't want to miss out on the first time to learn about the mysterious AdmiralityCode!

So Yun Qi and Iona took one of Bismarck's doppelganger dolls and carefully entered the deep cave on Yi 401.

This cave is obviously hidden more than 1,000 meters under the sea, not to mention sunlight here, even if you turn on the searchlight, you can't see anything ten meters away. But after entering the cave for about a kilometer, everyone magically discovered that there was a bright light in the cave.

It was a wonderful fluorescence that was cast from the surface of the cavern, making the whole cavern less dark and terrifying.

Seeing this wonderful fluorescence, Hinata frowned and said, "Strange, this is a special luminescent substance formed by nanomaterials. But strangely, the luminescent materials formed by these nanomaterials are not natural, but artificially manipulated! And the time is quite long!"

When Yun Qi heard Hinata's words, he couldn't help but answer: "It's a long time, how long can it be history." Didn't the sea fog appear sixty years ago?"

"Huh! How can the history of our sea fog be only sixty years!" Hearing Yun Qi's words, Hinata turned on the taunt mode again. Get ready to strike at the nasty ghosts that stand between you and your sister in all directions!

Looking at Yun Qi, who was ridiculed by Hinata, Iona actually took the initiative to defend Yun Qi.

"Hinata, can I tell everyone, Bismarck and I, as well as Yunqi, are very curious about this!"

As a loyal fan of her sister, Iona spoke, and Hinata had something else to say. Naturally, there is no end to knowing everything.

"Hmph, I said this at my sister's request. I'm not talking to you!"

"According to my tests, the structure of these nanomaterials is slightly different from the structure of the current nanomaterials, which should be the original structure from a long time ago. According to my speculation, these primitive nanomaterials are at least 100,000 years old!"

"What! 100,000 years!" everyone was surprised when they heard Hinata's speculation. 100,000 years is not a small number.

The record of human civilization dating back to its roots is at most 5,000 years ago. 100,000 years ago, human beings should have been ancient humans who drank blood!

In that era of ignorance, there would be a super black technology such as nanomaterials. What's going on here?

For everyone's questions, Hinata couldn't answer them. After all, this conclusion is a bit shocking. Nanomaterials do not appear in a vacuum. But there were nanomaterials 100,000 years ago, and this time span is really a bit amazing!

And as the crowd continued to go deeper, more and more surprising things appeared in front of their eyes. In this cave under the sea, there are very beautiful carved murals. And the frescoes are about to go deeper, the more detailed they are.

From these murals, Yun Qi actually saw humans fighting with some strange giant beasts. And this mural clearly looks like a historical record in flashback. It's just puzzling that most of the murals near the cave are engraved with the struggle of some primitive humans to survive. In the back, there were signs of human civilization, a large number of words of unknown meaning, and various strange-shaped buildings all over the cave. Yun Qi even spotted a mushroom cloud in a relatively backward position.

The huge mushroom cloud in the mural rises into the sky, and countless flames sweep the whole world. Countless human beings wailed in flames, and countless buildings collapsed. No matter how you look at it, it's a picture of the use of nuclear weapons. But according to Hinata, the mural is at least 50,000 years old. Because of the special nature of the surrounding nanomaterials, these murals are very well preserved.

Yun Qi felt as if he had inadvertently exposed the dark curtain of the sea fog world, and the human beings 50,000 years ago had the ability to make nuclear weapons, so why did they suddenly disappear. Could it be that they all perished in a nuclear war?

With these questions in mind, everyone rode the Yi 401 and continued to go deeper. And the frescoes found later completely shattered their worldview.

After going through the rather exquisite murals depicted in this section, Yun Qi and the others thought that there were similar murals in the back. It's just more polished. But the results were beyond their imagination.

The frescoes did appear again, but they were not carved. These murals were photocopied directly using nanomaterials.

In these murals made of nanomaterials, Yun Qi and the others discovered mental models for the first time. That's right, it's the mental model. Because the girls in these murals are not only extremely beautiful in appearance, but also have a special coat of arms specific to sea fog painted on their bodies.

One might think that these coats of arms may have been engraved by the maidens themselves, but the core of the mental model that appears on the belly of their bodies is an irrefutable proof.

Because of the meticulous depiction of these murals, everyone can recognize at a glance that these round spherical objects are the core of the sea fog's mental model. It is the most important thing that makes up a sea fog warship.