A sharp whistle reached them about an hour after they had begun searching the study.
They had uncovered a considerable amount of evidence of wrongdoing beyond what Rei had discovered, revealing just how deeply the mansion owner had been involved in crime.
Even setting aside the matter of the Underground Space, he would unquestionably be punished.
It was while Rei harbored such thoughts that the sound reached them.
The guards' response was swift.
"Rei, it's an emergency. This whistle is an urgent signal to gather immediately."
"Ah, come to think of it." Recognizing it as the same sound he had heard during yesterday's mansion search, Rei nodded at the guard's words. "Understood. So what exactly should I do?"
"We go to whoever blew the whistle. Come with me."
Ordinarily, the need to securely carry all the evidence found in the study would have slowed them down considerably. But since Rei had his Misty Ring, storing the documents inside meant the cargo wouldn't hinder him at all. He and the guards in the study burst out of the room without a moment's delay.
They ran straight toward the source of the whistle.
Along the way, they caught sight of what appeared to be the mansion's servants thrown into confusion by the sudden noise, but the guards kept running toward the direction from which the recurring whistle continued to sound.
Naturally, the others conducting the forced search of the mansion ran toward the source as well... and converged with Rei's group.
"Does anyone know what happened?"
"No."
The guards exchanged brief words. Since they were running, they wasted no further breath and kept sprinting through the mansion until they finally arrived before the guard holding the whistle.
"What happened?"
"I found a hidden staircase leading to the Underground Space — the same one they said was in the neighboring mansion yesterday."
It was a brief statement, but more than enough to understand why the whistle had been blown.
There were still some who hadn't arrived at the scene yet, but they too would be convinced the moment they heard that explanation.
"Where?"
"In this room. There was a mechanism in the bookshelf, and when I moved it, a hidden staircase appeared."
Listening to the guard's explanation, they entered the room.
One entire wall had opened up, revealing a staircase leading underground.
That staircase was a familiar sight to Rei.
Strictly speaking, it was different from the one he had seen yesterday, but perhaps because he believed it led to the same Underground Space inhabited by the pink tentacles, it struck him as the same kind of staircase.
"So this room isn't a study."
Tearing his gaze from the staircase, Rei muttered while looking around.
True to the claim about the bookshelf mechanism, the room contained several shelves.
It was perhaps too small to call a library, but it was undoubtedly a room for reading.
"So, what's the plan? If you're saying for certain it connects to the Underground Space, that means you went down the staircase, right?" one of the guards asked.
The man who had blown the whistle nodded.
"Yeah. Beyond this staircase, the Underground Space from the reports definitely spreads out. Though there were no tentacles, and no spatial rift either."
"Were there any corpses?"
Rei, who had been listening to the guards' conversation, suddenly asked.
From what he had seen yesterday, there should have been several corpses left in the Underground Space — reduced to nothing but bone and skin by the tentacles. The corpses of the Red Cloth members and the man who had brought them.
But the guard he asked shook his head.
"No, there were no corpses or anything of the sort. ...They probably recovered them."
Ideally, Rei should have recovered those corpses himself. But considering the pink tentacles' abilities, retreating at that time had definitely been the best option. If they had kept fighting, there was a high possibility that the number of tentacles would have continued to increase until they became unmanageable.
(Not just a possibility — it's safe to say it was almost a certainty.)
Beyond the spatial rift, there had been a presence of a vast number of the same tentacles Rei had fought. Considering that, he was confident that the decision to retreat from the Underground Space — without even taking the time to store the corpses in his Misty Ring — had been the right one.
"I see. If the corpses had been left behind, we could have linked them as evidence in this case. ...What do you think?"
The last person Rei asked was Vihera, who had entered the room with her presence suppressed — whether to surprise him or not, he couldn't say.
The others had been on guard, checking for additional clues in the room or watching in case tentacles emerged from the Underground Space. Despite all that, Rei hadn't noticed Vihera entering.
It would have been unreasonable not to be startled.
"Well," she said. "The neighboring mansion you went to yesterday had similar corpses, right? In that case, there's a good chance they'll be attributed to that side instead. ...Though if you'd brought back some tentacle remains like you mentioned, we could have made it work."
"No, that's just you wanting to fight the tentacles. Besides, whether 'tentacle corpse' is even the right expression, I don't know — but they turn to dust and disappear. How exactly am I supposed to bring back tentacle remains?"
"I trust that you'll figure something out, Rei."
"...Leaving it to me, huh. So, how was it? Did any strong enemies worthy of Vihera's enthusiasm show up on your side?"
"No. No one like that came. There were a few soldiers, but not as impressive as I'd hoped. ...Don't tell me they went to your side instead, Rei?"
A suspicious gaze was directed at him.
Ordinarily, anyone would have been captivated by Vihera's beauty, but since Rei was traveling with her, he was naturally accustomed to it and immediately shook his head.
"No, fortunately for you, nothing of the sort came this way. The only ones who came my way were the same sort of soldiers as the ones who went to yours. ...Though they were fairly competent, admittedly."
Rei briefly wondered whether they had been attacked like that yesterday because the mansion from yesterday had functioned as a place to preserve corpses, but he didn't voice that thought in front of Vihera. If he had, she might well have headed to yesterday's mansion — the neighboring one.
(No, if I consider that she's here on a request, she wouldn't do something like that. ...I hope she wouldn't, at least.)
With Vihera alone, it was accurate to say that he could never be certain what course of action she would take. Ordinarily, he could generally predict her behavior, but when it came to combat, there was a high chance those predictions would be wrong.
The guards who had been traveling with Vihera arrived a little later, peering in from outside the door. Leaving behind someone they were supposed to be escorting was honestly questionable, but... well, as Vihera had said, it was highly likely that there were no attackers like yesterday's in this mansion.
Thinking that and considering what they should do next...
"Wh-wh-wh-what is this!? Who built that staircase!?"
Suddenly, a voice echoed through the room.
As everyone in the room, including Rei, turned their gazes toward the source, they saw a man screaming with an expression of sheer astonishment right beside the door.
From that statement alone, there was no need to even think about who it was.
The mansion owner.
Rei had assumed the man was outside, taking out his frustration with some kind of action, but he never expected him to come directly into the mansion like this.
"Tell me! Was the reason you forced your way in to search this place because you were secretly building such a staircase!?"
Hm? Most of the guards and escorting adventurers who heard those words felt a flicker of doubt.
Rei felt the same way.
Judging from that statement just now, it was practically as if the mansion owner was saying he hadn't known there was a hidden staircase here.
For a brief moment, Rei wondered if the man was trying to cover things up because the staircase had been discovered, but from what he could see, the man still screaming as if to vent his frustration didn't appear to be doing anything of the sort.
He seemed genuinely, truly confused.
Of course, the possibility that it was an act couldn't be completely denied. But from what Rei could see, he didn't think the man was capable of such a thing, and above all, his behavior rang true.
(In that case, did he truly not know about this hidden staircase? That possibility wasn't something I hadn't considered, but...)
Even as the mansion owner, there was no guarantee he was intimately familiar with every corner of a mansion this large. Given that, it was probably not impossible to build a hidden staircase without his knowledge.
Naturally, such an undertaking would require considerable effort, and even if the mansion owner didn't find out, there was a high chance that people like the maids or the butler would discover it. To build such a hidden staircase without being detected under those circumstances — just how much effort would that require?
An extraordinary amount, without question.
But from what Rei could see, the mansion owner's astonishment didn't look like acting at all. There was a possibility that he was secretly skilled at performing, but if he considered things that far, he would have to cast suspicion on much more.
"What are you so surprised about? This is your mansion, so you should have at least known there was a hidden staircase here."
Rei said this as a probing question, but the mansion owner looked blank for a moment as if he didn't understand what was being said, and then a few seconds later, frantically shook his head.
"No! I had absolutely no idea that such a mechanism existed in my home! Who was it!? Who built this hidden staircase in secret, even from me, the master of this mansion!?"
At the way he screamed, not just Rei but even the guards wore expressions of doubt. As expected, it didn't look like he was acting or lying at all.
(Which means...)
Rei directed his gaze toward the maids, the butler, and the other soldiers and servants around the mansion owner, but all of them wore bewildered expressions. From what Rei could see, none of the people surrounding the mansion owner appeared to be involved in the hidden staircase matter.
Of course, it wasn't certain — there might be someone so skilled at acting that even Rei couldn't tell.
"The reason we launched this forced search is related to this underground staircase. ...Do you know what lies beyond it?" a guard asked the mansion owner.
But since he hadn't even known about the hidden staircase, there was no way he could know what lay beyond it. As the mansion owner shook his head, the guard continued with a stern expression.
"This staircase leads to a vast space spreading underground. I take it you naturally didn't know about the existence of a massive space beneath this mansion either, correct?"
"Y-yes. I know nothing about it. I've never heard such a thing at all."
The mansion owner answered immediately. He was probably thinking that he might be charged with some crime and subjected to a forced search over something like this.
Of course, even if he hadn't known about the hidden staircase, plenty of other evidence of crimes — more than enough to arrest him — had already been found. He himself unfortunately didn't seem to know that yet, and was likely thinking that if he could somehow muddle through this situation, everything would be fine.
"I see. ...The truth is, the space beneath this mansion is suspected of being connected to other mansions in this area through similar staircases."
"What!?"
Struck by shock once again, the mansion owner could do nothing but wear a dumbfounded expression.
Naturally.
If it had merely been connected to a space underground, there would have been things to think about, but he could have still accepted it. But if that underground space was connected to other mansions, that far exceeded the bounds of what was acceptable.
Depending on the circumstances, someone he didn't know at all might have been freely intruding into his mansion.
That was absolutely unacceptable.
"Who... who in the world did such a thing without permission! Whose permission did they—"
"Whoa."
As the mansion owner screamed, his face flushed bright red with anger, Vihera suddenly moved.
A short blade aimed at the mansion owner's head — she deflected it with her Hand Gauntlets.