This is ...... another great change of scenery.

　Looking at the base built on the fifth level of the "Sundial Forest", Sakura let out a cry of surprise.

　Some time had passed since that meeting, and the forest side base of the Hollow Bottom Fortress was taking shape.

　The 【Restoration】 of the building was almost complete, and now it was even at the stage of preparing the interior and equipment.

　The knights were flying instructions for the work, while the hired E-rank adventurers were running around to the right and left with supplies.

　At this rate, they could have the base in full operation tomorrow.

''Is Luke-dono working here again today?''
No, there's nothing left for me to do on this side of the border. From today, we'll be setting up the underground base. See, you're carrying the wreckage for [restoration] over there, right?

　From where I was pointing, a large amount of debris was being carried on carts to the base.

　Those things will be transported through the 'Dragon's Loophole' to the underground space side, where they will be [restored] and regain the shape of the building.

''I see, then it's the same as mine. Since today's request is to help you explore and secure the 'Demon King's Castle Realm'.
''Demon King's Castle Realm'' ...... I've been calling it 'underground space' for a long time now, so it feels strange.
I'm sure you'll get used to it.

　You and Sakura duck through the gate of the base and come to a large outdoor staircase.

　The "Dragon's Loophole", where the dragon once appeared and Noir fell, is a large hole in the cliffs of the fourth and fifth levels.

　Currently, a large staircase that extends straight up to the large hole and a cargo elevator have been installed, and the atmosphere of the past has been erased.

'Yes, let me see your pass!

　At the top of the stairs, a checkpoint was being held for people entering and exiting the large hole after stepping into it for a bit.

　The person in charge of the checkpoint was indeed not an ordinary adventurer, but seemed to be an office worker sent by the guild or knights.

''Speaking of which, Luke-dono. I remember that there was a dungeon gimmick door set up in this large hole, but I can't find .......
Actually, it's a lot of work: ......

　I couldn't help but smile as I remembered the anguish surrounding this great hole door.

''After the engineers and alchemists sent by the guild and the royal palace examined it, they found out that the door was still opening and closing as a switch for the breaking of the walls of the 'Thousand Year Corridor of the Abyss'.

　-- Someone who built the dungeon in the distant past created a robust labyrinth to protect the underground space from intruders.

　Furthermore, as a counter to attempts to force their way through the labyrinth by destroying it, they have prepared an automatic retaliation system that will unleash dragons on the ground - a system that will allow them to be used as a counterweight to any attempt to force their way through.

　That's the hypothesis the engineers came up with.

　A hypothesis is a hypothesis, of course. Of course, a hypothesis is a hypothesis, but it doesn't mean it's true.

　The alchemists believe that it is not someone from the distant past, but rather a device created by the Demon King Gandalf himself, and that its purpose is not to protect the underground space, but to prevent Mithril from being mined.

　In the end, the real story remains unknown.

　If the latter hypothesis is correct, then defeating and interrogating the Demon King might reveal the truth, but that's probably still a long way off.

'Even if we don't know why the trick was made, we only know the switch that triggers it ......, the next challenge will be to control the opening and closing, right?
Yes. If it doesn't open and close freely, it's useless as a passage.
By the way, they got tripped up big time there. The research didn't go anywhere.

　As I descend down the 'Dragon's Loophole', which is easily accessible on foot, I continue to recount the events of just a few moments ago to Sakura.

　Of course, I'm not talking about anything that could be a leak of information.
　I'm thinking about the content after being properly careful.

I even came up with the idea of me taking the walls apart and opening and closing them, but of course I refused with all my might. I don't want a lever to open and close.
...... Oh, maybe. The door has been [disassembled] by Lord Luke, hasn't it?
'Correct. So, His Majesty the King, who was numb, ordered that if the door can't be moved as he pleases, it should be broken. I've kept the remnants, so we can [repair] it anytime, but for the time being, it will remain a doorless cave.

　If you're thinking about the defensive side of things, it's better to have a door.

　However, His Majesty had said that the original door was out of control, so they would have to build a new door later on by normal means.

　While they were talking about this, they finished descending the slope and arrived at the end of the 'Dragon's Loophole'.

''What kind of land is the 'Demon King's Castle Realm' ...... beyond this?'''
'This is the first time Sakura has been here? I haven't seen one since I [disassembled] a huge door on this side. Pretty awesome sight, huh?

　Outside the cave, a scene that didn't look like the bottom of the ground was all around us.

　Rock mountains and wasteland as far as the eye can see.
　A ceiling of rocks that emitted a light that could be mistaken for the sky.
　A river of spring water flowing through the valley.

　The "Dragon's Hole" is connected to the rocky mountains near the walls of the underground space, and the other side of the underground space across the ravine is being developed as a mine for the demon race.

　However, because the underground space is so vast, it's impossible to even see it with the naked eye without using skills.

''What a ...... such a place was under the ground. ......
'The ground-like spaces themselves are found in various dungeons, but they're rarely this large.

　Whether or not the Demon King Gandalf is aware of the existence of the loophole is a matter of opinion even among those involved on our side.

　But when the underground space is this vast, the optimism that even the Demon King doesn't have a grasp on the whole thing is convincing.

''Come to think of it, Luke-dono. Wasn't this the habitat of dragons, as I recall?　I haven't felt any sign of her at all since a moment ago.
Yeah, that's half the reason.

　Translucent, light green, monument-like objects placed at the four corners of the proposed base construction site.

It's an oversized boundary stone. If there were four boundary stones like that, even dragons wouldn't be able to get to them so easily.
Warding stones: ...... I've never seen the real thing before.

　Sakura approached to the very edge of the fence surrounding the boundary stone and stared at its surface.

'I've heard it's a stone to ward off demons, but I haven't met many adventurers who carry it around with them. Is it very valuable?''
It's a consumable item, and only a limited number of alchemists can synthesize it. And since there are restrictions on how it can be used, it's usually only used when it's needed most.

　Restrictions on the use of ward stones.
　That is, due to the fact that it interferes with the magic flowing through the earth to form a ward, it can only be used if it is resting on the ground.

　Even though it is called the ground, it does not mean that it has to directly touch the earth, but it can be used on the foundation or the floor of the labyrinth.

　However, if there is a human body or other living organism's body in between, it will not be effective at all.

　Also, if you move it forcibly, the link with the earth's magic power will be broken and the effect will be interrupted.

　-- In other words, the boundary stone cannot be used while carrying it around.

''I see. So it's an item suitable for defending a base or camp safety measures? Then what's the other half of the reason?''

　Just as he was about to answer Sakura's question, a single dragon roared across the sky.

　Its body was torn apart in the blink of an eye, and it fell into a ravine with a splattering of blood.

''I think I just saw someone on the back of a dragon: ......
'He's half the reason. He's the Dragonslayer, Theodore Beaufort. He's an eccentric guy who came from a noble family and became an adventurer because he wanted to fight dragons.

　Theodore was one of the high-ranking adventurers I approached.

　The man and I didn't have a good relationship, but when I contacted him because I thought he would change his eyes if he heard the word "dragon," he flew in before anyone else.

I'm going to get to work then. Once I've built a base here, I'd like to live more comfortably as a weapons dealer this time.
You seem to be enjoying yourself, though, don't you? Have you been stimulated by the sight of an unknown land?
It's stimulating. ...... I wish I could say I was stimulated. I feel like I'm back on track.

　Saying goodbye to Sakura as she goes to work on her patrol request, I decided to start repairing the underground base of the Hollow Bottom Fortress.

　If I can get this done, Green Hollow Town and the Sundial Forest will be safe again.

　After that - we'll think about it when it's over.