Klaha felt a bit incredulous.

She confirmed that what her hand had grasped was indeed a single block of the floor, which at first glance seemed seamless.

With a feeling of "Wait, it actually opened?" she turned to look at Ziel and Dewey.

“……Whoa.”

“Ancient ruins are so freaking cool~~~!!”

The two long-legged men expressed their amazement in their own ways as they strode swiftly over, making full use of their long strides.

They crouched down.

“Whoa, this is it.”

“Whoa! It really is!”

“It is, isn’t it?”

The three of them were in complete agreement.

Most likely, even if someone else had been there, they would have said the same thing. It was just too perfectly placed.

Removing the floor panel revealed a small recessed storage space.

And right there, almost as if it were inviting them to press it, was a control panel similar to the one in the aquarium room, marked with symbols indicating "open" and "close."

This is it, Klaha thought.

This is exactly what Wilae was looking for.

“I’ll go get the others,” Ziel said before heading outside.

That left Klaha alone with Dewey.

“…Hey, that thing.”

“…You’re curious too, right?”

The button was one thing.

But their gazes were both drawn elsewhere.

To the strange, silvery, glossy substance next to the button.

“What is this?”

“Probably magisteel alloy.”

Magisteel alloy.

Klaha knew about it.

Unlike ordinary metals, it was a term for special metals harvested in dungeons or areas with high magical density. Their properties and processing methods varied, but in general, they were highly reactive to magic, making them valuable materials for weapons, armor, and magical tools due to their extreme durability.

The most familiar example she could think of was from her time in Next Apex, where Godach, the leader, wore armor made from such an alloy.

But—

“This looks like a liquid, though.”

“Yeah. Mercury-based, maybe?”

“Hold up a sec.”

Dewey left the room briefly.

He returned carrying some kind of instrument.

“What’s that?”

“Toxicity check. Just in case… Nah, this isn’t it. What the hell is this?”

“Should we take it back for analysis?”

“Hell yeah. Think we can move it? Try not to touch it with your hands if possible.”

“I’ll give it a shot.”

Klaha exchanged a glance with Dewey, who had prepared a storage container.

“Move.”

“Oh?”

The magisteel alloy slid smoothly into the container, far more effortlessly than expected.

“……?”

Something about it felt off to Klaha.

“Whoa, Klaha, that was smooth as hell. You’re better at this than most mages.”

“No, it just… felt like the magic worked a little too well.”

“Maybe it’s highly magic-reactive? In that case, handling it could be—”

“Brought them.”

Before Dewey could finish, the familiar voice reached Klaha’s ears.

Looking towards the entrance, the remaining five members had arrived.

“Seems we weren’t off the mark after all.”

Wilae stepped in first.

She took a glance at the discovery, nodded in satisfaction, and said,

“Does anyone want to press the switch?”

She waited three seconds.

When no one volunteered,

“Eh—”

“Whoa, hey—”

Without hesitation, she pressed it.

Klaha and Dewey reflexively flinched back at her boldness.

Immediately afterward, a clunking sound echoed—like a lock being undone.

Then came a deep rumbling, like the earth shifting.

“Now, let’s go check our answer.”

Wilae, already seeming to know where to go next, strode off.

Ziel had lost count of how many times he had seen something awe-inspiring today.

“This place is massive. Professor Wilae, is this the control room?”

“Control room?”

Roylen’s muttered words caught his attention, and he kindly explained further.

“Yes. Well… where should I begin?”

It was a huge room.

Even compared to the aquarium room, it was just as vast.

So far, this was the largest space they had discovered in these ruins.

Long tables and chairs were arranged in rows.

It was the kind of place that could easily accommodate a hundred, even two hundred people.

As Wilae led the way, she immediately began working at one of the desks, prompting Ziel to start a discussion with Roylen.

“Did you notice anything odd about the switch in the aquarium room, Ziel?”

“Yeah, I guess.”

Thinking back, he recalled,

“Like how the symbol was too simple, or how it felt weird that I could even operate it.”

“Good observations. I had the same sense of unease. And there’s a reason for that.”

“A reason?”

Recalling his earlier conversation with Klaha and Dewey, he added,

“Like… maybe it was designed to be opened in the first place?”

“…I’m impressed. Ziel, have you ever considered becoming a ruin-exploration escort? I think you’d be really good at it.”

Being genuinely praised like that, Ziel hurried to downplay it.

“Wait, no, that wasn’t just me thinking—”

“Oh? Sounds like Ziel just found his future job.”

Lililia sidled up to them.

“Yep. It’s decided. Ziel is ours now.”

“Then the church will take his right half.”

“Can you not talk like I’m about to be split in two?”

Feeling slightly overwhelmed by the sudden talk of employment, Ziel urged Roylen to continue.

Roylen obliged.

“To put it simply, yes. These places, including this control room, were designed to be opened easily.”

Casually, he added,

“But doesn’t making them easy to open mean they’re not that important? We were talking about that earlier.”

“Not necessarily. In some cases, ‘places that must be opened’ also exist.”

For example—

Before he could continue—

Wuoon.

A strange sound, like the flapping of a giant bird right by his ear, cut off Roylen’s voice.

“Whoa.”
“Oh—”
“So, seeing is believing, huh?”

Right in front of them.

A massive, completely white wall.

On it, an unfamiliar pattern had distinctly emerged.

It seemed that Wilae had successfully manipulated something. Perhaps she was projecting it with light magic? Just as that thought crossed Ziel’s mind, he realized something. He couldn’t understand its meaning, but there was something familiar about the arrangement of these patterns.

“Is this... writing?”

“That’s right.”

A voice responded casually from behind. Eunice.

“Though, it seems to be a different language from the one I was using earlier. Maybe the designer or the intended users didn’t speak the Unified Ancient Language? It’s said that, unlike today, multiple languages were used in prehistoric times, so this could be one of them...”

“I can read the characters decently, but I don’t understand the terminology. What about you, Roylen?”

“I have no clue. But,”

Eunice nodded in agreement.

The two of them turned their gazes to one particular figure standing in front of the inscriptions.

“If it’s Professor Wilae, she can probably do it. After all, she’s the vice director of the Grand Library.”

Ziel, meanwhile, was completely lost.

All this information was being thrown at him at once. So, multiple languages existed in prehistoric times? Huh. He had figured there’d be some difference between ancient and modern languages, but even within that era, there were multiple tongues? Wouldn’t that have been inconvenient? And even Eunice, Lililia, and Roylen couldn’t read this? Interesting.

“Vice director of the Grand Library?”

It was only after sorting through all of that that the question finally left his lips.

“That’s the kind of position that can do this kind of work?”

“Yeah. The Grand Library was originally established by the first Arcmage, the Mage of the Book. Its primary purpose was to preserve the advanced magical civilization of prehistoric times. These days, it’s more well-known for certifying Arcmages and managing the Magic Federation’s organizational groups, but in its original role, deciphering ancient scripts like this is a core duty. Prehistoric documents are extremely rare, so each one is highly valuable for deciphering. I’ve studied a bit under Professor Wilae, but my reading speed and comprehension...”

“Still don’t compare to hers,” Eunice finished.

At the front of the room, Wilae was still focused on the glowing interface, continuing her manipulations.

“…For the record, I can’t read a single word.”

“If you could, that would be impressive. We’d have to reserve a seat for you in the Grand Library.”

Eunice chuckled.

“But, I overheard something earlier. You might have been exactly the kind of person they designed this place for.”

The conversation circled back to an earlier topic.

Ziel furrowed his brows, trying to piece together the hint.

“You mean it’s a ‘design that transcends time’?”

Dewey slung an arm over his right shoulder.

“Mmm,” Eunice murmured, leaning against his left shoulder as if to counterbalance Dewey. What is this? Ziel thought, but the two ignored him and kept talking.

“Honestly, I’ve never designed something with that level of foresight, so I was like, ‘Huh, neat.’ But since Ziel was able to open it, doesn’t that mean it was made that way on purpose?”

“Exactly. It’s more reasonable to assume this was designed so that ‘even someone from a completely different culture, with no knowledge of this place, could operate it’ rather than thinking Ziel just ‘happened to’ open it by chance.”

Ziel could understand that.

That logic made sense. There was no way he had some kind of genius intuition that just happened to work here. The more natural conclusion was that there were ‘guiding elements’ in place, making it accessible to anyone who encountered it.

But—

“I don’t really get it either,” Lililia said casually.

That made Ziel feel a little relieved. At least he wasn’t the only one.

“Right?”

“No, I actually understood everything. Ziel-kun is the only one who’s lost.”

“Then explain it to me.”

“I don’t need to. Eunice-kun, go ahead.”

Ziel felt the urge to call her out on that, but at this point, he just wanted to move the conversation forward. He turned to Eunice.

“Why go to the trouble of designing it to ‘transcend time’?”

At this point, Ziel no longer thought this was some insignificant space that ‘anyone could access.’

Even now, Wilae was reading through vast amounts of text and performing some kind of magical operation he couldn’t comprehend. If that was the case, then this place was likely what Roylen had described earlier—a ‘place that would cause problems if it couldn’t be opened.’

So then—

“What kind of place is this, for such a design to be necessary?”

“My guess is actually pretty simple. In fact, it’s exactly what it seems to be. ‘A place that would cause trouble if, far in the future, someone like you came and couldn’t open it.’”

It took Ziel a moment to process that statement.

Because, in other words—

“Are you saying this space was designed under the assumption that ‘future people’ would visit it?”

Klaha picked up where Ziel trailed off.

Ziel turned to look at her. She had been watching Wilae’s operations with shining eyes earlier, but at some point, she had joined their discussion.

It was an instinctual reaction. She had been drawn in and spoken up without thinking. Eunice nodded, and this time, Roylen looked at Klaha—and at Ney, who stood beside her.

“That’s the most logical conclusion. There are several clues pointing in that direction. For example—Ney-kun.”

“Ugh.”

“‘Ugh’ is not an answer. Did you notice any design elements in Ziel’s story that seem to account for language barriers?”

“Ugh, a pop quiz?”

She groaned in displeasure.

She stared straight at Ziel, making him flinch slightly. Then—

“The red and yellow lights were obvious.”

“Good. Why?”

“They’re warning colors. Red, and then yellow when combined with black. The two patterns might be there as a safeguard since some people might have trouble distinguishing red from black.”

She added, almost as an afterthought—

“Not that I know for sure. We don’t know if human color perception was the same thousands of years ago. Oh, and those weird sounds, too. Loud noises function as danger signals for living creatures as long as things like thunder exist.”

"Well, that's my assumption, but I believe that, beyond what Ziel conveyed to us, various non-verbal warnings had been issued. However, some of them may have lost their effectiveness over time when directed at us, while others—the ones Ney just pointed out—may have retained their function as 'warnings' due to their high universality."

"Oh," Ziel nodded.

"Oh."

"……"

"Ziel, are you okay? You’re not about to explode, are you?"

"...No."

Hearing that, he felt an urge to carefully examine his memories—had he overlooked something, failed to hear something, or perhaps even missed a scent?

But he quickly shook off that thought and said,

"Go on."

"Then, I'll take you up on that. That's why Professor Wilae mentioned 'doors without magical locks.' If they were considering visitors from such a distant future, they would naturally have accounted for the possibility that the magical key system might change and lose compatibility. In that case, it would be preferable to have management sections with physical locks."

"Yeah. Some magical locks can last for thousands of years, after all. In that sense, physical locks, which someone like you could just kick down, have greater universality and preservation in terms of unlocking methods."

"By the way, Eunice, how much prehistoric magic has survived into the modern age?"

"Since we don’t even know the exact scale of prehistoric magic, I can’t say for sure. But the fact that so few people hold the title of Arcmage might itself be an answer."

Just as Ziel hesitated over whether to ask Eunice, "What do you mean by that?"

Or just as Klaha was about to ask Roylen, "Is there a reason we can conclude this wasn’t simply for non-literate users but was specifically aimed at the future?"

"Oh my, it seems the role of detective has been completely stolen by the students."

Wilae.

She had slowly made her way back to them.

"Sorry, I got caught up in the discussion."

"No, it’s fine. It’s been a long time since I last gave a lecture to a large group. I was already finding it difficult to keep talking at length. But—"

She snapped her fingers.

"From here on, I’ll take over."

Woon, woon.

A deep humming sound echoed from outside the control room.

"Follow me. I’ll clear up your questions."

Wilae started moving again, heading out of the control room and back into the spiral dome.

Ziel, along with the other seven, followed her, thinking to himself how her assertiveness reminded him of Eunice.

The change became apparent as soon as they stepped outside the room.

"That large door over there—"

"It’s open. Judging by the height... roughly at ground level—"

"An entrance. Or in this situation, we might as well call it an exit."

Picking up from Klaha’s words, Wilae spoke calmly.

"Naturally, the facility’s original users didn’t enter and exit through the water channels. Most likely, they didn’t even consider that future intruders like us would take this route."

The sound of their footsteps echoed through the spiral tower.

Slowly, she rounded a hallway.

"The design of this place makes more sense if you assume entry from the ground-level entrance. There were no physical switches to open the water-side entrances, but there are several installed along this path. That suggests they designed it with automated guards in mind while ensuring emergency routes were simple."

Like loosening the front door’s lock while keeping guard dogs inside.

Ziel tried to interpret it that way, though he wasn’t entirely confident.

"But this raises the exact question you all were just discussing."

Why?

Without hesitation, she passed through the large door.

Beyond it was another vast, open chamber. At the far end stood yet another enormous door—so tall that even Ziel doubted he could force it open with sheer strength. A towering metal door.

Before that door, in the center of the hall, Wilae stopped in her tracks.

"Why would they do that? Why would they deliberately structure the facility to be 'solvable'... Klaha."

At the sudden mention of her name,

"Y-Yes!"

"You asked why we can assert this was intended for the future."

"...Yes. I thought we couldn’t rule out the possibility that, back when this facility was operational, non-literate individuals simply worked here."

"Your question is valid."

She acknowledged it with a gentle tone.

"It could have been an era of low literacy rates. Or perhaps many workers here were unfamiliar with the language used within the facility. Since we can’t rule out that possibility, yes, Roylen and Eunice’s hypothesis is nothing more than a romanticized theory. But, my apologies—I took a bit of a shortcut earlier."

"A shortcut?"

"I saw it. The writing left behind in the control room. Words that indicate what this facility is. But explaining it in words would be difficult to grasp. That’s why we came here."

"Think about the original path of entry. The automated guards. The warnings that rang and shone within the water chamber. The pictorial explanations of operating methods. Thoughtful designers like them—where would they most want to leave their warnings? Where would they convey what this facility is, and how?"

She continued,

"Naturally, it would be in the first place people lay their eyes upon."

Ziel, along with the other seven, slowly turned to where Wilae had been looking.

There, on the wall, covering it entirely—

A massive painting.

A dragon.

"A dragon.

A being that should not exist. A creature that can only exist through the power of magic... or perhaps a great being conjured by our imagination. A symbol of power."

"Anyone who sees this would grasp the danger of this facility. And any perceptive mage would, upon seeing the surroundings of the structure they first laid eyes on, deduce the meaning of this symbol."

She snapped her fingers.

Once again, the sound of doors opening echoed.

This time, it was accompanied by an even stronger light.

The light of summer. The inner doors beyond the great entrance began to open, allowing a flood of brilliant illumination to pour through. A pure white light that revealed everything.

Before their eyes—

"This ruin is an energy facility.

A massive structure that has maintained its concealment through prehistoric magic for thousands of years. An extraordinary, long-forgotten mechanism that, by connecting to the ley lines, provides humanity with a stable supply of magical power.

Its name—

Heaven and Earth in Harmony."

Through the bright blue sky, piercing ever upward—

They beheld the towering form of an impossibly massive tree.

(End of Volume 3, First Half)