The sea could be seen within the forest.

It wasn’t some drunken hallucination. It was, without a doubt, reality.

"Z-Ziel-san—look at that!"

Klaha was tugging insistently at his sleeve beside him. It was an excitement she would never usually show. But Ziel understood how she felt. After all, there was no way to stay calm.

What spread before them was an expanse of blue.

It was nothing like the landscapes formed by clusters of trees in the eastern mountains where they had recently been. It was completely different.

The trees that met the eye—each and every one of them—seemed unique.

Their stems were different. Their branches were different. Their leaves were different. Even their roots, breaking through the soil to bask in the sunlight, varied in dryness, dampness, thickness, and twists. The summer flowers scattered across the greenery were vivid as if painted by a rainbow, reflecting the sunlight in dazzling brilliance.

And then came the most astonishing sight, after they had walked a while from the research facility.

When Ziel, leading the way alongside Klaha, reached their destination, what awaited them was a vast downward slope.

And to their amazement—

Beyond the vivid forest, a boundless, undulating sea stretched out before them.

"That tree… its head is completely submerged in seawater…! It’s like it’s inside the ocean—"

What Klaha pointed out was, of course, something Ziel had already noticed.

Beneath the surface of the water—within that glimmering shoreline—a forest floated like a mirage. This wasn’t just the moon’s reflection shimmering on the water. Even from here, it was clear. Even if one were to reach in and stir the water, the trees wouldn’t disappear.

Because just as Klaha had said—

"—It’s like there’s a forest inside the ocean."

"I’m glad to see you’re pleased."

A voice responded from behind, and with a rustle, a man stepped forward.

Ziel recognized him, of course. They had met yesterday, and he had traveled with them this far.

Silver hair. Polite demeanor. The distinguished pharmaceutical mage conducting research from this southern hidden sanctuary—

Roylen.

With a theatrical gesture, he placed a hand over his chest and gave a small bow.

Behind him was the unchanging summer blue.

The lush forest. The sea that ran through the heart of that lush forest. The sky and the forest’s green reflected on the water’s surface. And beneath that water’s surface, a quiet, second forest submerged in blue.

As if standing against a grand backdrop, as if playing the role of a stage guide, he spoke.

"You’ve walked a long way to get here, so allow me to formally welcome you.

This is the Southern Sea of Trees—one of the last great mysteries of this world.

Welcome to this southern hidden sanctuary, where the trees and the sea intertwine."

Ah, so that’s what it is, Ziel thought.

As if those words had given him an oddly satisfying sense of understanding.

For a brief moment, on this first day of exploration, he recalled the events that had led him here.

"Our primary goal is to identify the source of the 'Tremor'—the epicenter."

Roylen made this statement in the dining hall after breakfast had settled.

The room had enough chairs to seat twenty or thirty.

When Ziel casually inquired about it during the meal, he learned that the facility occasionally invited adventuring parties for survey expeditions, and the space was arranged with that in mind.

The wide room, filled with summer breezes and morning light, felt crisp and refreshing, as the day's heat had yet to rise.

Roylen stood in front of a board that Ney had wheeled in. Pinned to it were several maps and planning documents. Knowing that he wouldn’t grasp the finer details, Ziel quickly decided to have Klaha decipher them for him. For now, he sat beside Lililia, tasked with an important duty—stacking the clean plates she had meticulously washed.

"I’ve conducted a preliminary survey to the best of my ability. However, due to the nature of the Southern Sea of Trees, it’s difficult to gather precise data."

"Because of the many 'Mana Spots' scattered throughout, correct?"

"Indeed. Your understanding is quite sharp, Klaha-san."

Like an excellent student, Klaha supplemented Roylen’s explanation. Ziel had already heard her theories on the matter the night before.

The Southern Sea of Trees.

It wasn’t a 'Labyrinth.' There were no signs of 'structuralization' caused by the stagnation of circulating mana. However, over a hundred known 'Mana Spots'—pockets of accumulated, non-structuralized mana—had been confirmed in the region.

Combined with the area’s natural terrain, exploration difficulty increased exponentially.

While it was unclear whether it rivaled the highest-difficulty labyrinth, Abyss, its sheer complexity and vastness were daunting. Only about one-fifth of the region had been successfully mapped, and even that portion changed daily due to the influence of the 'Mana Spots.'

Ziel had been briefed on all this beforehand.

"Ziel-kun, are you perhaps interested in tower construction?"

"Huh? No… well, yes. It seems I was."

"Be sure to divide the materials and build multiple towers, lest civilization collapses in pursuit of heights beyond its reach."

Following Lililia’s words, Ziel carefully disassembled the towering stack of dishes before him.

Time moved forward, and so did the discussion.

"But thanks to our new support team, our situation has changed significantly. Until now, due to the high difficulty of exploration, we primarily conducted surveys in the outskirts. However, now we have a team that has conquered the most challenging labyrinth.

With them, we can ignore obstacles and conduct optimal investigations as needed."

"Ah, just letting you know in advance! Leaving the professor aside, Dewey and I are weaklings, so please don't count us as part of the combat team. We'll be coming along, but just keeping up will be all we can manage!"

A voice, clearly meant to grab attention, called out—Ney, Roylen's assistant, standing beside him.

"Got it," Lililia replied casually, and Ziel nodded in return. For a brief moment, his eyes met Ney's. When he gave another small nod, she mouthed a quick "thanks" before looking away.

"So, should we assume that for efficiency’s sake, there might be situations where engaging in combat is the better option?"

"Yes, that’s right. Unlike a labyrinth, the surroundings here are open in all directions, so we do have the option to take detours. But, as Klaha pointed out, it’s a matter of balancing efficiency in terms of stamina and time."

Something soft and unexpected pressed against Ziel’s hand.

He had been distracted by the discussion of combat, his attention away from what was in front of him. Realizing he had unconsciously touched something, he glanced down to check.

"Oh, sorry about that. I finished washing the dishes, so I thought I’d help stack them too."

It was Lililia’s hand.

"......I’m really sorry."

"Why do you sound so genuinely apologetic? I said 'sorry' out of habit, but I don’t actually feel bad about anything."

"Oh... No, I mean, yes. Sorry."

"You’ve turned into an apology puppet."

Klaha gave a nod, seeming to approve. Not because she had picked up on Ziel’s slight emotional wavering, but more likely because she was simply following Roylen’s explanation and processing their plan. Probably. Maybe.

She then followed up with another question.

"How long is the investigation period expected to be?"

"That’s actually a tricky issue. I assume for adventurers, a cycle of attacking and taking breaks on a monthly basis is the norm..."

"Yes, that’s generally the case."

Ziel listened in, focusing on his hands while keeping his ears open.

"The problem with the southern sea of trees is that if we leave for a whole month, the terrain could change drastically. Not only would we have to start from scratch after an interval, but..."

"There’s a chance we’d lose our way on the return trip and get stranded."

"Here we go again," Lililia murmured beside him.

Ziel wanted to argue that they hadn’t even set out yet, but if he acted all reasonable and dismissed the danger now, she would absolutely bring it up later if they actually did get lost. Instead, he simply responded, "Let’s hope that doesn’t happen," in a calm tone.

"Right?" Lililia smiled, and Ziel decided this was the best approach going forward.

"For now, we’ll proceed while keeping an eye on the situation."

"Understood. Of course, we’ll need to consider both the stamina of those handling combat and the progress of the investigation. We can decide as we go."

"Got it," Klaha replied, noting something down in her notebook.

"All done," Lililia said, spreading her hands open. Before them, a neat stack of sparkling clean plates shone as if brand new. Looking at the sheer number of them, most people would assume, "That must have been one crowded cafeteria—probably so packed that some had to eat standing up."

Ziel, who had eaten only a modest portion himself, glanced at the dishes and suddenly thought of something.

"What about meals?"

He muttered quietly, making sure only Lililia could hear.

"Oh, good point. Let’s ask. Hey, Professor Roylen!"

The whole point of whispering was lost.

Roylen flinched slightly at the sudden call but quickly composed himself. "Yes? What is it?"

Ziel noted how quickly he recovered. There was definitely something to learn from that.

"So, about this 'attack'? How do we handle meals? Is Ziel going to carry everything himself?"

"Hey."

"You can do it, right?"

"...Well."

It wasn’t like she was wrong.

Compared to everyone else, Ziel’s stamina was on another level. If all he had to do was walk at their pace, even with a heavy load on his back, he wouldn’t so much as break a sweat.

But Roylen chuckled and said, "No, that won’t be necessary."

"We’ll bring some emergency rations, but for the most part, we’ll be sourcing food on-site. I can identify edible materials myself."

"Ohh."

"Thank you," Lililia said with a nod.

Then, she leaned in close to Ziel’s ear and whispered, "Sounds fun, huh?"

Ziel wasn’t sure why she suddenly switched to whispering, but since he was happy about it, he decided not to question it.

"In that case,"

Klaha picked up where the conversation left off.

"Our primary luggage will consist only of investigative magic tools?"

"Ah, no, actually—about that, we have—"

"Heyyy, delivery for all your equipment needs~!"

Roylen had just begun to explain when three figures entered the room.

Dewey, the blond magic tool engineer, struggled in with large bags slung over both shoulders. Behind him was Wilae, arms raised near his shoulders, ready to catch him if he stumbled.

And finally—

With violet hair and starlit eyes, a strikingly well-featured Arcmage.

"What the hell is that, Eunice?"

"Heh heh heh... Well, obviously—"

Rather than carrying an oversized backpack, Eunice let it float weightlessly in front of him, using magic.

With a playful wink, he pressed a finger to his lips.

"That’s for you to find out when we get there."