The responsibility felt enormous.

“Come on now, don’t be so tense.”

“Yeah. Besides, what Eunice said is still just a prediction.”

From the right, Lililia spoke. From the left, Ziel chimed in.

“Exactly. Besides, the real investigator here is Roylen. Just think of it as lending a small hand.”

“By the way, when Roylen-sensei says ‘help’ in his lab, it usually means ‘you get paid for doing nothing.’”

From behind, Dewey and Ney’s voices chimed in.

“Shall we start a serious discussion about salary reductions now…? Well, putting that aside, we are relying on you, but as everyone says, you don’t need to overthink it.”

“If there’s magical concealment involved, Klaha might have a hard time noticing it. This is a team effort. Let’s take it easy.”

Even as Roylen and Wilae spoke these words, their sharp gazes were already scanning the surroundings.

Because of that—or maybe not—Klaha followed their lead, letting her gaze wander as well.

They were deep in the forest.

At the farthest reaches of the southern country, near the sea—so much so that nearly half the area was submerged underwater.

The air, the plants, the animals—so abundant that if one were to start counting them all, they might exhaust the history of humankind before finishing.

And yet, faint traces of human existence still remained.

“Huh,”

She locked eyes with the last person to arrive—the one who had insisted on coming here.

He still looked uncertain, slightly troubled, as if he was still trying to figure things out.

“L-let’s do our best… okay?”

The mysterious air he had during their first meeting was nowhere to be found. Instead, he clenched both fists tightly, speaking with determination.

“…Yes! I’ll do my best.”

Klaha found herself answering without hesitation.

The prehistoric ruins.

Once again, the eight of them had come here.

Even after the rain had stopped, the two hadn’t shown up at the drying area. That’s when Klaha thought, Ah, they must be lost again. That was her usual assumption. Because of that, she was a little late in finding them this time.

Even if Eunice was with them, if they had gotten lost, they were probably indoors—at least, that’s what she had assumed.

When she spotted them through the window in the hallway, the first thought that came to her mind was, What are they doing? Facing each other, talking about something with serious expressions. She had opened the window, but hesitated—afraid she might be interrupting.

“Ah,”

Ziel noticed her hesitation.

Muttering something like “perfect timing” under his breath, he raised a hand and walked over. Eunice followed, slightly behind him, as if slipping into his shadow.

Klaha recalled their earlier conversation—before the thunder rumbled and the rain started falling. It had been brief, but different from their past interactions. The walls between them had thinned, or maybe even disappeared.

“We figured it out.”

“…Huh?”

Maybe she had been lost in thought, or maybe she had braced herself too much. Whatever the reason, she couldn’t grasp the meaning of Ziel’s words right away.

What did he mean?

Borrowing Lililia’s way of thinking, she wondered if it was something like, Klaha isn’t someone to be feared. If that were the case, it would have been nice.

But it wasn’t.

“The reason why we can’t pinpoint the source of the ‘tremors.’ And also, what exactly the prehistoric ruins in the southern jungle are.”

It was something completely different.

The information he had just thrown at her was far more valuable than she had expected, making her thoughts freeze.

Eunice smacked the back of Ziel’s hand, saying, “That’s not exactly what I said,” but after hearing the details, Klaha thought Ziel’s summary wasn’t far from the truth.

“A ‘station’…? I can’t really picture it.”

“Yeah. I don’t know anything about old modes of transportation either.”

It wasn’t that they were useless, but…

Ziel and Lililia, while the other six were busy with their investigations, were simply staring blankly at the walls.

It had been four days since Eunice’s discovery.

After the scheduled break, after laying out a normal investigation plan, after waiting through Eunice and the others’ discussions with the map spread out—

They had finally arrived at their target.

The prehistoric ruins.

No one knew who built them or why. A place that had lost its purpose long ago, appearing merely as a hollow shell.

Or perhaps… it really had been just a shell.

Eunice had thought of it when looking at the lab—standing like a box, shielding them from the rain.

“Maybe from the beginning, it was nothing more than an empty box, built to protect against the elements… What do you think, Lililia?”

“About what?”

“Does it sound plausible? I feel like the climate was quite different back in prehistoric times.”

Lililia’s eyes widened.

“You know, Ziel, you’re surprisingly knowledgeable about this stuff. You know that climate changes over time?”

“I’ve picked up bits and pieces. Seeing how the environment shifts depending on whether there’s a labyrinth or not, for example.”

“Ohh, I see.”

She nodded, convinced.

“Hmm, I don’t know. It’s called ‘prehistoric’ because there aren’t many records from that time. If it’s not mentioned in the scriptures, I wouldn’t know much either. Wilae-san might, though.”

“Ah, yeah.”

Ziel nodded, looking for Wilae. But since she was deep in discussion with Eunice, he gave up.

“Guess we’ll find out by investigating.”

“You’re pretty reserved, Ziel.”

“Can you stop discovering new sides of me?”

“It’s not really—”

Mid-sentence, Lililia’s gaze shifted elsewhere.

Ziel followed her eyes.

“Oh,”

Klaha was there.

She was clearly watching them, hesitant.

“Excuse me. I’d like to examine that wall. Is now a good time?”

“Being reserved seems to be contagious among traveling companions…”

“Not at all. I’ll step aside right away. Go ahead.”

“And I am ignored…”

While Ziel and Lililia bantered, Klaha promptly began her work.

Watching her, Ziel thought, Maybe this is where she truly belongs. If she could focus on her surroundings like this, there must be far more she was capable of.

Even as he was thinking, Klaha was already making progress.

“Lililia-san, I’d like your opinion.”

She stopped, placing her hand on a specific spot on the wall.

“Hm?”

“What comes to mind when you think of a dragon symbol?”

“Ah, that.”

She muttered instinctively—because she had seen it before.

Wings. Limbs. Fangs. Claws. A legendary creature, rarely ever seen in the form of a magical beast, and never appearing before human eyes.

The mark of a dragon was etched there.

“A dragon, huh. And this person beside it…?”

A sudden pat on the shoulder made me flinch unnecessarily.

“Right now, that reminds me of the Great Beast Disaster. Klaha, do you think that mark is a clue to something?”

“Yes. It’s been on my mind for a while. I’ve visited several ruins, and this dragon mark is present in all of them. Even if it’s not a direct link, I believe it could be a clue to something.”

“Oh, so you really fixated on that, huh?”

Dewey, who had just been lying flat on the ground with his ear pressed to the floor, joined the conversation. Seeing dirt on his blond hair, Ziel quickly brushed it off with his palm.

“Thanks. I’ve been curious about it too, ever since I heard Uni-chan’s story. It got me thinking…”

“Thinking what?”

“What if this place is a shelter or a refuge?”

He shrugged, as if to say that’s how it seemed to someone as physically weak as himself.

Ziel figured he was probably remembering what had happened four years ago.

“I don’t know much about prehistoric times, but weren’t there tons of magical beasts back then? If so, it wouldn’t be strange for a place like this to exist.”

“That makes sense… But if it’s a refuge, that means there were people around who needed to take shelter, right?”

“Yup.”

“Then isn’t it weird that only this building remains? If people lived here or used this place, there should be remnants of other facilities—houses, for example.”

“Maybe those just decayed over time, and only this sturdy structure survived.”

“Ah, I see.”

Ziel found himself convinced, but not everyone was.

“I wonder. If that were the case, wouldn’t the dragon motif have a stronger message of threat?”

Roylen had approached without anyone noticing and offered a counterpoint.

“A message of threat?”

“According to your theory, the dragon is a ‘threat,’ and this place was built to protect against it. But the dragon mark doesn’t have an ominous feel to it. To me, it looks more neutral—”

“Professor! Are you just going to stand there chatting while making your assistant do all the work?”

“This isn’t chatting. It’s deduction and explanation.”

“We’ll be discussing a pay cut for you later, Professor.”

“Why do you have any authority over my salary?”

Ney’s voice called out from a distance.

She had been crouching down, examining the floor just as Dewey had earlier. Now, she straightened up and announced,

“There’s no way this is a shelter.”

“Why not?”

“If you saw a cage in the forest with a bear symbol on it, would you think, ‘Wow, this place is safe!’ and walk right in?”

She turned back to the floor, adding, “That’s just absurd.”

Two seconds of silence passed before Dewey suddenly said, “Alright, time to get serious,” and hurried over to her. Roylen followed, muttering something about a “wild bear Dewey,” before giving him a pat on the back.

“They’re an odd bunch. Is that some kind of performance?”

Lililia made a cryptic remark.

“If this were meant to be a shelter, the symbol would probably be something more recognizable. Maybe something like ‘Dragon’s Sky’?”

“‘Dragon’s Sky’…”

“It’s just a random association. But, Ziel, have you heard of it? Something like this?”

“No. Is it a place name?”

“Nope. A fairy tale title. It’s pretty famous, actually. I’ve even used it for storytelling sessions. It’s been around so long that no one knows when it originated. Not that I think it’s directly related.”

“Oh, but—”

Klaha took those words in and said,

“It’s simple and easy to understand. Something that stands out in its surroundings, or even more simply, a symbol of power. At the very least, I’d say those kinds of images have been shared across generations.”

“So what does that mean, Professor Klaha?”

“Prof… Ah, well, let’s see. Power, power…”

“Speaking of power, there’s Ziel.”

Ziel thought, That title is way too much for me.

Meanwhile, Klaha, who had experience as a problem-solver in the Eastern lands, seemed to be feeling the weight of expectations. Ziel noticed her shoulders were a little tense.

Trying to lighten the mood, Ziel said,

“Maybe if I hit it, it’ll open. Like this—”

“Whoa!!”

“Huh!?”

“That scared me… I thought you were about to destroy all of prehistory, Ziel…”

“I’M the one who got scared…”

Honestly, if it were that easy to figure out, some adventurer would have discovered it long ago. This thing just begs to be hit.

Suddenly, Lililia, who had startled him with her loud voice, rapped the dragon mark with her knuckle. Then, realizing, she quickly withdrew her hand. “Ah, wait, I shouldn’t. It’s basically a cultural artifact.”

Now that she mentioned it, she was right. Even if it was deep in the southern jungle and abandoned, it was still a valuable ruin. Being careless with it wasn’t a good idea.

“……There’s a sound.”

But—

Even after the two of them had pulled their hands away, Klaha continued tapping on the dragon mark.

“Dewey! Are you free right now?”

“Huh?”

Called upon, Dewey stood up again.

“If a cute girl calls me, I’m always happy to respond… What is it? Did you find something?”

“Do you have a spare vibration detector?”

“Yeah, yeah. Where do you want it?”

“On the wall.”

“The wall?”

Even as he questioned it, Dewey immediately moved. But before he could get there, Ney arrived with a bag and placed it on the floor. “Today’s work is done,” she declared.

Ziel had no idea what was going on, so he just watched.

Klaha conferred with Dewey, and as they attached the device to the wall, she patiently tapped along its surface.

“…Doesn’t it seem odd?”

“Yeah, something’s off. Hey, Ziel! Help out for a sec.”

“What?”

“Push against this spot—not too hard, just enough to make it shift.”

“Got it.”

Ziel pressed against the designated area with steady force.

Watching, Klaha and Dewey both nodded in understanding.

“Eunice!”
“Uni-chan!”

They called out in unison.

Eunice looked surprised for a moment, as if he hadn’t expected it. But then, together with Wilae, he rushed over.

“Did you find something?”

“The vibrations here are strange.”

“The internal structure of the wall seems different. It’s not exactly hollow, but—”

Eunice gently placed a hand on the dragon mark.

He closed his eyes.

“There’s a magic circuit inside.”

“I didn’t notice because there was no residual magic,” he muttered quietly.

“Give me a second… The protection is heavy. The ignition point is pretty far, and the activation node is even—”

“Do you need a circuit analysis? If it’s hard to perceive, I can create a physical model for reference.”

“Hmm… That might help. But the way this is set up, if we channel magic into it, the aged parts could burn out… Professor, we should preserve it as is for the future, right?”

“Depends on the type of magic circuit. If necessary, I could handle the software, and Dewey could take care of the hardware for repairs.”

“Why do I feel like I’m being burdened with unrealistic expectations from an older woman…?”

“Gross.”

Before long, the last remaining member, Roylen, also joined the group.

He must have been trying not to interrupt the conversation. Standing next to Ziel, he looked at him, silently asking, "Did you figure something out?"
Ziel nodded, as if to say, "Apparently so."
Beside him, Lililia also nodded. "It seems so."

"Do you know the exact location of the activation point?"

Klaha asked.

"Hmm. More or less. It looks like it's connected downward, after all."

"Then, instead of taking a magical approach first, shouldn't we try pinpointing the physical location? For example, Dewey’s—"

"Oh?"

"If the theory about it being a shelter or evacuation site is correct, then even if the magical infrastructure shuts down..."

"There might be a physical way to unlock it."

Klaha nodded. "Yes."

Understanding her point, Eunice also nodded. "Yeah."

"Let's give it a shot... Ah, thank you, Klaha."

"...! No, I'm just glad I could be useful!"

Eunice gave an embarrassed smile, while Klaha's face lit up like a blooming flower.
Watching them, Dewey nodded approvingly. "Ah, the beauty of youth..."
Ziel stared at him, thinking, "What's with this guy?"
Then, beside Dewey, Ney commented, "And what exactly is your role in this?"

"Alright, Klaha, could I leave the task of pinpointing the exact location to you? I'll analyze the circuit structure and have Wilae adjust the scale for me."

"Understood. I actually mapped out the area when I was here before, so I'll compare it with that."

"I'm counting on you," Eunice said.

He then placed his palm on the dragon emblem again and murmured some numbers and units.

"I can't let myself fall behind," Wilae remarked, picking up on the numbers.

The sand at their feet stirred slightly. Instead of leisurely reacting to it, Wilae was already assembling something.
As if guided by an unseen will, the sand gathered in her hands, forming complex stone-like carvings.
Three lines extended from a single starting point, branching and merging intricately, stretching deeper and downward, creating a miniature magical circuit.

Klaha studied it while holding her self-made map.

Eventually, she pointed at a spot on the map.
"I think... it should be around here."

"Oh, this looks promising," Roylen said, peering over her shoulder.

With their two guides leading the way, the party began to move.

They arrived at what appeared to be an unremarkable location.

Beyond a large chamber, they had passed through a somewhat winding hallway and emerged into a broad corridor.
Eunice tapped on the wall—seemingly just another ordinary wall, aside from its unusual material.

"It’s not hollow. So I don’t think we’re entirely off track."

"The activation point is on the lower side, right?"

Klaha stood beside him, showing the map.

"So... like this. There's space here, so to the sides..."

"Wait, isn't that a bit too dynamic?"

"Too much?"

"...No, but let's try it out. Ziel, could you give it a go?"

"I'm free too," Lililia interjected.

"Alright, then Lililia as well," Eunice said.

Ziel and Lililia stood side by side in front of the wall.

"Can you try pulling it apart to the sides?"

"Where exactly?"

"All of it."

"All of it...?"

"Like, just—grab the whole thing and go 'zzzzgghhh'?"

Lililia suggested. Ziel had no idea what she was talking about.
Eunice nodded. Ziel had no idea what he meant either.

"Here, Ziel, grab this part."

"Where?"

"Wherever you feel is right."

"Man, when a saintess speaks, it really hits deep."

"Stop saying random things," Lililia shot back.

"Am I?"

Ignoring Lililia and Dewey’s pointless chatter, Ziel placed his fingers in a suitable groove, as instructed.

"On three, okay?"

"Got it."

"One, two... three!"

Wait, weren’t we supposed to go on 'three'?

With that thought lingering, Ziel pulled to the left with full force.

Of course, the wall didn’t budge.

But—

"…? This feels different."

"Yeah, the texture is off."

"Should we try with more effort? Just as a test."

"I might as well. 'Behold! The strength of one who liv—'"

"Whoa, whoa, wait a second!"

Seeing them roll up their sleeves, Eunice hastily intervened.

"Don’t break it! This is valuable. …But it does seem like it’s moving."

"Yeah. But I don’t think the entire wall is shifting. It feels lighter than that."

"Did it feel like a locked door? Like when you pull on one with an internal lock?"

When Ziel nodded, Eunice went into thought.
He glanced at Klaha’s map. Roylen pointed at a spot.

"So, if this part is partially hollow..."

"Ah, I see. You mean there might be a sliding mechanism?"

"…That could be it. I think I hear some distant echoes..."

"I see, I see," Eunice nodded.

"Then, Klaha was right. Ziel, Lililia, could you step aside for a moment?"

"Sure.""Go ahead."

Having finished their task, the two of them moved to the back.
Lililia lowered her rolled-up sleeves.
She then glanced at Ziel’s sleeves and silently helped him roll them down as well.
"Thanks," Ziel murmured.

"What’s the plan now, Eunice?"

"Ideally, we’d find a way to open it physically, but no adventurer before us has figured it out. And frankly, that sounds tedious. Let’s take a shortcut."

With that, Eunice crouched down.
Right below the spot where Ziel and Lililia had placed their fingers.
He ran his hand across it.

"The absence of residual magic means the original magical locking system is no longer functional.
That system was heavily protected, so reactivating it would be a hassle.
But if we understand the physical structure, we can slip magic in from a different angle—"

A soft, purple glow seeped from between his fingers.

He closed his eyes, smiled slightly—

And with a snap of his fingers—

"Well, that should do it."

With a loud rumble, the wall began to move.

How many years?
Decades?
Centuries?
Or even millennia had it remained sealed?

The long-forgotten wall remembered its purpose as a door.
It split apart, sliding away to the sides.
The hollow spaces prepared to hold the moving segments were filled, revealing a new void in exchange.

Large enough to hide four people standing abreast.

At a glance, it seemed like the corridor had simply extended a bit further.

But when they looked downward—

"...I see."

Dewey murmured.

As if summarizing why the group of eight had struggled in the southern jungle.

"With something like this underground, no wonder the calculations didn’t make sense. No matter how we measured the tremors."

A vast, submerged underground passage.

Where did it lead?
How far did it stretch?

It gaped open before them, leading into a deep, dark unknown.