"Hm? Rei? What's wrong?"
With most of the camp already asleep, an adventurer who was still awake chatting noticed Rei stepping out of the Magic Tent and called out to him.
Rei answered without making much of it.
"Just couldn't sleep. Honestly, after the jellyfish commotion yesterday, I should be tired enough. Anyway, I'm going to take a walk and do a quick patrol toward the Treant Forest with Set—change of pace."
"Huh? You're taking Set? Hmm, I'd rather you left him here, if possible. Come on, Rei?"
The adventurer frowned at the idea of Rei bringing Set along.
It wasn't possessiveness toward Set—though he couldn't claim that feeling was entirely absent, either. The bigger reason was that Set would be the first to sense anything if a monster emerged from the lake.
They did have a night watch posted, but it was a fact that Set could detect enemies faster than any lookout.
...The one in their party who usually acted as their bandit had actually been a bit sore about that, too.
Still, even a Beastman couldn't match the sharpness of Set's senses. The gap in raw ability was simply too wide.
"Sorry. But if I say I'm heading out on patrol, Set's going to want to come along anyway. You'll just have to bear with it."
At Rei's words, the other adventurers could only fall silent.
They understood that Set was Rei's tamed monster. Pushing the issue would only put him in an awkward spot.
"Grrul!"
And sure enough, Set purred energetically, as if to say he was absolutely going with Rei!
The adventurers relented, telling him to come back as soon as he could.
A few Lizardmen outside didn't make any fuss either. Even though they couldn't understand the words, they could read the situation well enough from watching Rei and Set.
...If Zozo had been there, he probably would have asked to tag along. And if Gaga had been around, he might have come along just to kill time.
"Alright, then. Let's go. A stroll through the night sky."
"Grrrul!"
Once Rei settled onto Set's back and gave the word, Set let out a happy cry. After a few running steps, he beat his wings and soared into the sky.
Once they were some distance from the Birth Tower, Rei called out to Set.
"Set, head in the direction I point."
"Grru?"
Set let out a slightly questioning sound—wasn't this supposed to be a change of pace?—but with nowhere in particular he wanted to go, he followed Rei's instruction and kept flying.
A little over ten seconds later, they reached the spot where the Woodcutters would be working during the day.
What are we doing here? Set gave Rei a puzzled look. Rei stroked his head and spoke.
"Grimm, are you there?"
"Grru!"
Evidently not expecting Grimm's name to come up here, Set let out a surprised cry.
But before Set could purr a question—what's going on?—the space warped, and Grimm materialized from within.
"It has been a while since we met face to face."
Grimm said with a nod.
His demeanor might have inspired nothing but fear in some, but Rei, who shared a fairly close relationship with Grimm, could tell that he wasn't trying to threaten or intimidate him. He was genuinely looking forward to seeing Rei in person.
To Rei, Grimm was an Undead—but also someone who had advised him through all sorts of matters. Meeting him directly like this was a welcome occasion.
"Yeah, it's been a while. We've been talking through the Paired Orbs fairly often, though."
"Hmm, true enough. We were conversing just moments ago, even. Thinking on it, it is a strange thing."
Grimm nodded in understanding, but he couldn't stand around doing that forever. He surveyed the area instead.
Rei's group was at a spot where the Woodcutters had finished felling trees—still quite far on the outer edge of the Treant Forest as a whole.
Even so, Grimm seemed to sense something. He looked around, nodded in satisfaction, and lightly tapped the ground with the ferrule of his staff.
It wasn't a sharp strike aimed at attacking the ground. He simply tapped it with the tip, and from that point, like ripples spreading outward, something—magical power, most likely—propagated through the surroundings.
Rei couldn't sense magical power himself, but he understood that what Grimm had just done was essentially a radar using mana. The only reason he could follow it at all was probably because Grimm had intentionally made it so.
Set, Rei's tamed monster, also understood that Grimm had done something.
The people at the Birth Tower were skilled, but Grimm as an Undead was in a league of his own.
For that matter, even if they were skilled adventurers, they weren't mages.
The ability to detect what amounted to a magical scanning radar—like what Grimm had just performed—was essentially nonexistent among them.
"...I see."
Several seconds after tapping the ground, Grimm finally spoke.
What is it? Rei turned his gaze toward him, but Grimm simply remained silent.
Several more minutes passed.
"Ho."
That sound slipped from Grimm's mouth again.
The faint surprise in his voice meant that something had startled even 'that' Grimm. For Rei, that was far from reassuring.
It almost made him think they'd found something outrageous—some object, or perhaps some being.
"Grimm, what happened?"
"Hmm. The Treant Forest, you said? Beneath the center of this forest, something is alive... or alternatively, something exists."
"Alive? Exists? ...I'm pretty sure we dealt with whatever originally created this Treant Forest."
"I understand how you feel. But do you doubt my abilities?"
"That's..."
Rei knew full well just how extraordinary Grimm was.
Enough that if asked who was wrong—himself or Grimm—he'd lean toward himself.
And right now, with no evidence of his own to offer, contradicting Grimm's words was difficult.
"Grru."
Set, listening in on their conversation, purred.
He was clearly interested in what Grimm had to say.
"So? Do you know specifically what's down there in the center of the Treant Forest?"
"Unfortunately, my magic is not so convenient as all that."
"...I'd say it's plenty convenient."
The Treant Forest was larger than even the lake that had teleported there.
Tapping a staff from the outer edge and performing a quick spell had been enough to reveal that something existed beneath the forest's center.
He might not have known exactly what it was, but the fact that he could pull that off at all was, from Rei's perspective, nothing short of extraordinary.
In the first place, Rei could basically only use Flame Magic.
That was why Grimm, who could wield all manner of magic, was someone he envied.
(Though if it's limited to Flame Magic, I don't intend to lose to him.)
Grimm directed a somewhat exasperated look at Rei's demeanor. He was a skull, so he had no eyes, but the atmosphere made his exasperation perfectly clear. Painfully clear.
"What?"
"My magic is certainly more varied than yours, that much is true. But you possess enough mana to be worthy of succeeding Lord Zephyle, do you not? That burning thing over there—that is your magic, is it not?"
From the mention of burning, Rei caught on to what Grimm was getting at.
"The Slime?"
"A Slime? So that is the true identity of that perpetually burning entity."
"Yeah. It came out of the lake—a Slime from another world. Ridiculously huge. I tried to kill it with Flame Magic, but it just keeps burning without any sign of dying."
He paused there, thinking that maybe Grimm could do something about the situation.
The Slime's enormous size made it more than adequate as a light source, but having a massive burning Slime right next to where everyone slept was not exactly comfortable.
However, if he carelessly meddled with the burning Slime, there was no telling how it might react.
If so, having someone skilled in magic like Grimm deal with it would be the best option. Or so was Rei's thought—his whim, really.
"Hmm. A Slime from another world. Whether it's interesting... it certainly is interesting, but..."
"Then could you take it off my hands?"
"...Don't ask the impossible. Something that large—what am I supposed to do with it?"
"Well, if you're saying that, the winter Eyeball was just as huge, wasn't it?"
"Which is precisely why I can't take it in right now. However... yes. I shall search for a location that can contain that Slime. Once such a place is found, I'll have no objections."
This was Grimm being soft on Rei.
Even if it was impossible now, he was promising to take the Slime in once he found a place to contain it.
Of course, it wasn't that he was unconditionally soft on Rei.
The existence of a Slime from another world had genuinely piqued Grimm's interest as well. That was an undeniable fact.
There were Slimes in this world with various special abilities too, but the moment the words "from another world" were attached, it inevitably became more intriguing.
"Then for the time being, storage... storage it is. In any case, once you find a place to store that Slime, I'd like you to take it. ...Assuming it hasn't burned out by then."
"I can't deny that possibility. If it were a Slime from this world, I could roughly estimate when it would burn out. Well, in the first place, it would normally burn out instantly from your magic."
As the two chatted, Set, perhaps bored, purred and pressed his face against Rei.
Pay attention to me—Set's behavior made the demand clear.
When they'd first met, Set had been quite wary of Grimm, but now he showed no such caution whatsoever.
From Rei's attitude, he probably understood that Grimm wasn't a threat.
"Fohofo. Set seems to be getting bored, so let's leave the talk about the Slime here. More importantly—what will you do? Will you head to the center of the Treant Forest?"
"Hmm. Now that things have gotten this big, I'm torn on whether I should just settle it on my own."
If this had been back when the Lizardmen first arrived, he would have handled it himself without a second thought.
But with Gilm itself now deeply involved, he hesitated over whether it was something he should resolve on his own judgment.
If it were just a matter of reaching the center, he could follow the trail the Gigant Turtle had left behind.
"That's not something I can decide for you, but... whether you intend to destroy it or wait, wouldn't it be best to at least go see the source first? Whatever you decide to do about this matter, knowing where the enemy is can't hurt, can it?"
Put that way, Rei had no choice but to agree.
Nothing concrete had been decided about how to handle the situation yet, but whether he chose to destroy it or not, there was no guaranteeing the mastermind—or whatever was causing all this—wasn't right there.
"You're right. Then let's go. ...The center of the Treant Forest, huh. Another troublesome place. What in the world is going on? I'm pretty sure I investigated it thoroughly when the previous incident was wrapped up."
"Who knows. Perhaps the ones who investigated failed to find it. Perhaps someone entered after the investigation. Perhaps something was brought in. ...Or perhaps the mastermind behind this incident was among those who investigated."
Grimm's words carried a weight that was hard to dismiss.
But precisely because of that, Rei honestly hoped they didn't apply this time.
His best-case scenario was simply that the original investigators had missed it, or that the cause of this incident had arrived after the fact.
With that thought, Rei asked Set to carry him.