Jellyfish.
They were creatures that naturally existed in the sea.
In reality, there were freshwater jellyfish on Earth as well, but to Rei, jellyfish were creatures that lived in the sea — or so his perception went, and he had never known otherwise.
The jellyfish currently in his line of sight were unquestionably swimming in a lake.
Not only that, though he had no idea how, there were also jellyfish flying through the air.
Their sizes varied wildly — the small ones were about palm-sized, while the largest were even bigger than Set.
True to the phrase "all shapes and sizes," numerous jellyfish swam through the water and air, their entire bodies glowing.
"This is... honestly amazing."
"Gruu."
At Rei's words, Set purred as if in agreement.
Despite Rei and Set being right there, the swarm of jellyfish showed no signs of attacking.
It was a scene that made him wonder whether they were even aware of his and Set's existence.
(Are they monsters...? Or maybe, just like the Lizardmen, they simply aren't hostile toward us?)
Gazing at the jellyfish shimmering in the night, Rei pondered this.
At the very least, the jellyfish drifting nearby showed no sign of attacking.
"Can you understand me?"
Rei called out to them, almost as a formality.
But the jellyfish showed no sign of responding.
Even so, they did not attack — they merely drifted near Rei and Set.
(So they don't understand language. The Lizardmen couldn't understand us at first either, so that's not particularly strange. But the fact that they aren't attacking us — does that mean they're inherently peaceful monsters? ...Though "peaceful monsters" feels like a contradiction in terms.)
Rei thought this while watching the jellyfish drift through the air and water. In reality, monsters with low aggression did exist.
Whether the jellyfish drifting around him were the same was something he questioned as he considered what to do.
If they truly showed no signs of hostility, then it would be fine to simply leave them be.
"Set, what should we do? Think we should head back to everyone for now?"
"Gruru? Gruru."
In response to Rei's words, Set purred, wanting to stay here a little longer.
For Set, the beautiful sight spreading before his eyes — a spectacle that could even be called fantastical — was something he wished to keep watching for as long as possible.
That said, given the current situation, he couldn't exactly do so.
Eventually they would need to go inform everyone about the true nature of these jellyfish, but just a little... truly just a tiny bit longer, he wanted to watch.
Normally, Rei should have said something to Set in response.
Given their current situation, the sight of glowing jellyfish near the Birth Tower could easily inspire fear precisely because they were unknown.
The jellyfish floating in the water and air each had different glowing parts.
Some had spheres of light darting around inside their transparent bodies, while others had light in the shape of bands rather than spheres, and some freely changed shape within the jellyfish's body.
(I remember seeing illuminations like this on TV... This is, in a way, a natural illumination. No, not natural — a living illumination?)
Rei was momentarily at a loss for what to say to Set as he watched the jellyfish flying around him, when suddenly one approached.
Even seeing it come closer, Rei didn't feel the need to be on guard — likely because even he couldn't bring himself to feel hostility toward the fantastical creature.
For just a moment — truly just a moment — he wondered if this was merely a ploy to let his guard down, but even when the jellyfish came right up beside him, close enough that not only could he touch it by reaching out, but he would brush against it merely by shifting his body slightly, it showed absolutely no sign of attacking.
"Ohh."
The jellyfish that approached was a relatively large specimen, with its umbrella measuring about a meter across, and exceeding two meters including its tentacles.
The large jellyfish moved about beside Rei, rubbing its body against him as if nuzzling affectionately.
It was almost the same behavior Set showed when being clingy with Rei.
"Hey, can you understand me? Seemed like you couldn't earlier."
Rei murmured, but the jellyfish still showed no reaction.
"Um, so... you really don't understand? What should I do about this... ah, I know."
Bewildered by the jellyfish pressing against him, and feeling something indescribable from the sensation, Rei called out to Set.
Set looked at him as if asking what was wrong, but Rei spoke while still tangled up with the jellyfish.
"Slowly, slowly head toward the shore. If you do, maybe this jellyfish will come along with us."
"Gruru."
At Rei's words, Set purred softly in acknowledgment and, following the instruction, slowly flapped his wings.
Even while hovering above the lake, Set had been flapping his wings.
He slightly increased the speed of his wingbeats... slowly changed direction, and began moving toward the shore.
Just as Rei had predicted, the jellyfish that had been rubbing against him showed no particular displeasure and moved along with them.
Normally, Set could not carry anyone other than Rei on his back.
A child might be manageable somehow, but with a two-meter-long jellyfish on his back, flying would be out of the question.
Yet now he was flying without any problem at all — precisely because the jellyfish wasn't actually riding on Set's back. The jellyfish itself was flying through the air.
Thanks to that, no weight burden was placed on Set, and he could fly normally.
"Oh."
Seeing that jellyfish begin to move with Rei and Set, about ten others followed along.
It wasn't that the jellyfish clinging to Rei was the boss of the glowing swarm.
At the very least, there were several other jellyfish larger than the one attached to him.
(Do they have factions or something? Or is it something else entirely?)
Rei felt a slight twinge of puzzlement at not understanding the jellyfishes' behavioral principles, but given the situation, he judged it wasn't a problem and continued toward the shore.
When they had first flown to where the jellyfish were, it had taken only seconds, but now Set was flying slowly to match their speed.
As a result, it took several minutes to reach the shore.
"R-Rei?"
As they neared the shore, a voice reached his ears.
The slight tremble in it was likely because of the jellyfish clinging to Rei.
Or perhaps the speaker simply thought Rei had been possessed by it.
Since the jellyfish was glowing, the sight of Rei wrapped in the creature was clearly visible once they approached the shore.
"Yeah, it's me. Anyway, it's clear that these jellyfish can glow and fly through the air, and they definitely don't have any particular aggressiveness."
"No, but... are you really sure?"
From the adventurer's perspective, Rei presented an extraordinary sight — wrapped in a transparent jellyfish with glowing parts.
Seeing such a figure, even if told he was fine, he couldn't readily nod in agreement.
But in reality, Rei was perfectly fine.
When he lightly tapped the jellyfish clinging to him as if giving a signal, it seemed to understand and simply detached.
Once it separated, the jellyfish — flying through the air just as before — possessed a beauty more than enough to captivate those watching.
This was true not only for the adventurers, but for the knight and Lizardmen as well.
Even Zozo and Gaga had their eyes stolen by the sight of multiple jellyfish flying... no, swimming through the air.
"This is... incredible..."
Exactly who murmured that, Rei couldn't tell.
But that anyone who witnessed the scene before their eyes would utter such words was something he could fully understand.
That said, the spectacle that only Rei and Set had witnessed earlier — where far more jellyfish than those that had followed here were swimming through the air and water, glowing all the while — was even more fantastical than the scene now before them.
That was why he could watch with more composure than the others.
(Still, what exactly are these jellyfish? Seeing them glow like this, are they calling companions with their light? ...Though what they'd do after calling them, I have no idea.)
What the jellyfish were doing. What they were thinking. What they were feeling.
Rei had absolutely no idea.
That said, as long as he didn't think they possessed high intelligence, he could safely assume this was instinctual behavior.
...What specific meaning that behavior held, however, remained as unclear as ever.
"Hey, Rei... these jellyfish... they don't have any hostility toward us, right?"
One of the adventurers suddenly asked.
For the Adventurer Man, watching the jellyfish drift as if dancing before his eyes, their fantastical beauty likely made him uneasy.
Perhaps they were using this beauty to draw the attention of those watching, only to do something in that opening — or so he might have been thinking.
In truth, Rei could sympathize with the sentiment.
It would be a lie to say the same thought hadn't crossed his mind.
But even so, the jellyfish that had grabbed onto him at the lake had shown no sign of doing anything.
With that in mind, Rei's judgment was that they were probably fine.
Of course, that was merely what Rei thought, and there was a very real possibility that things were different in reality.
"I think it's probably fine. When I actually went to check on the lake, nothing happened to me, right? The jellyfish that came here are far fewer than the numbers I initially saw. That's why I don't think there's any need to worry about that."
"Even more jellyfish than these..."
Watching the murmuring adventurer, Rei suddenly realized.
The adventurer before him knew what a jellyfish was.
Gilm had rivers nearby, but no sea.
In other words, anyone who had grown up in Gilm should never have seen a jellyfish before.
There was a possibility he had heard about them from someone, though.
(In that case, this adventurer is the type who came to Gilm on his own.)
That wasn't particularly strange.
These days, a huge number of adventurers had come to Gilm seeking work, but before the Expansion Construction began, only a handful confident in their own skills had made the trip.
Considering that he was an adventurer entrusted with guarding the Birth Tower as a skilled hand, it was reasonable to assume he was one of those early arrivals.
Though it didn't particularly matter either way.
Or perhaps he had seen the flying jellyfish that were said to rarely appear in winter.
"These jellyfish... they're technically monsters, right?"
"Probably. Though they're monsters that don't have Magic Stones."
In response to the question from the adventurer who knew about jellyfish, Rei answered thus.
The monsters in this lake did not possess Magic Stones.
At the very least, the lizard monsters had absolutely none, no matter how thoroughly they were examined.
If so, the way to distinguish between a monster and an ordinary creature would ultimately come down to whether it could do things ordinary creatures could not — in this case, a jellyfish flying through the air.
That said, that was only a distinction from Rei and his companions' perspective.
By the common sense of Japan that Rei knew, a jellyfish flying through the air was impossible. But this lake itself had likely been teleported from an entirely different world — not from this one, nor from the world where the Gran Dragonia Empire existed.
Perhaps in the world from which this lake had come, jellyfish were creatures that lived in freshwater and could fly freely through the sky, and it wouldn't be strange at all.
(Is that a bit of a stretch?)
Rei couldn't entirely dismiss his own thought as unreasonable, but actually watching the jellyfish flying before his eyes made such concerns seem irrelevant.
Seeing them fly like this, he didn't need to overthink it — simply watching the jellyfish before him, the sight of them drifting through the air, was satisfying enough.
Just how much time had passed... eventually, the jellyfish dancing through the air — perhaps satisfied with their display — departed from before Rei and the others.
Every single jellyfish that had been dancing followed the first one as it left, trailing right behind.
Ah... someone watching the jellyfish dance let out a disappointed voice, but whether the jellyfish heard it or not was unknown.
In any case, the swarm vanished from before Rei and the others, returning to the center of the lake.