There were over twenty hours of minor earthquakes and atmospheric rumblings.
Signs of a new dungeon's birth.
Immediate investigation requested.
That was what was written on the posted request at the "Bent Corner Inn", an adventurers' lodge in the Ohadano region, east of the Kingdom of Sepans.
Up until now, in the entire Kingdom of Sepans, there had only ever been one dungeon, the "Never-Go-Hungry Dungeon," which had existed for nearly 140 years and spanned eight floors.
It didn't yield especially valuable treasures, but monsters occasionally dropped food items, making it well-known as a dungeon suitable for long-term stays.
To be honest, it wasn't a very profitable dungeon in terms of income.
Even so, if one stayed on the eighth floor for an extended time, they could still earn a decent amount and get some good training.
In fact, there's even an official adventurer rank promotion exam in the Kingdom of Sepans that requires a one week stay on the eighth floor of that dungeon.
Still, because it was geared toward intermediate adventurers, it wasn't very popular with high-level ones.
And for the past forty years, there had been no sign of growth or change in that dungeon.
Since the newly emerged dungeon had just appeared, no one expected much profit from it yet.
But it had to be determined whether this dungeon would bring prosperity or disaster to the kingdom in the future.
On the same day the request was posted, two veteran adventurers did a quick scouting run and returned.
Their report was simple: a brand-new dungeon with nothing remarkable, except that deep inside, there was a spot where hot water, like an onsen, was bubbling up.
Several days later.
Two female knights were riding on horseback, heading slowly toward the dungeon.
They were on a follow up investigation to verify whether the dungeon matched the contents of the initial report.
"I'm hoping it's exactly as the report says, just a plain dungeon."
Said one of the knights, who had a laid back demeanor.
The other, who seemed to be her senior, responded…
"You mean, you don't care if the dungeon doesn't benefit the kingdom?"
"Well, you see, senpai~ if a dungeon with big profits shows up, rogue fortune hunting adventurers would come swarming into the country, and the peace would deteriorate, right?
The adventurers would be thrilled, sure, but we're civil servants, you know~. Even if a profitable dungeon pops up, it's not really a good thing for us~."
"…Haah, you're as nonchalant as ever… but you have a point. Twenty years ago, a new dungeon was discovered in the distant Kingdom of Kenma, it dropped high-grade gems. But with all the degenerate adventurers flocking in, public safety has been steadily declining."
"…We've arrived."
At the entrance to the dungeon, something had been carved into the stone.
"Onsen Dungeon."
"Eh? …Who carved this?"
"Who knows…? The report only mentioned that there was an onsen inside. Maybe the first adventurers who investigated it carved this?"
"I can't imagine any veteran adventurer would just go carving signs into a dungeon. Well, whatever. Let's investigate."
Venturing inside, they encountered familiar weak monsters like bats, rats, and insects typical of a dungeon's first floor. They easily defeated them and pressed forward.
"These monsters don't drop anything, huh~?"
"So it's the no-drop type…
That would mean we'll need to look for treasure chests or treasure rooms, maybe?"
"Or maybe the only thing here is the onsen?"
"…That would be ridiculous. I've never heard of a dungeon like that."
After about three hours of thorough exploration, and checking every corner.
There was really nothing but an onsen.
They had to fight through a few weak monsters to get there, but that was it.
"…I'm sweating."
"…Yeah."
"Wanna dip in the onsen?"
"…Is that safe?"
"Well, the adventurers in the first investigation suspected it might be dangerous, so they brought back some of the water. They had it tested, and there were no toxic substances found."
"Then… let's go in."
"Yay! Let's go in!"
They had ridden for hours to get to the dungeon, then spent hours walking inside. they were dripping with sweat.
On top of that, they hadn't gone to a proper onsen-or rather, had a proper bath-in a long time. Truthfully, they wanted to get in one so bad that they could hardly stand it.
Taking a bath during a mission might seem questionable for a knight…
…but this was a legitimate part of the dungeon investigation. They would bravely risk their bodies for the sake of the kingdom.
They removed their armor, stripped naked, and kept their swords within reach.
They were slightly worried about other adventurers suddenly appearing, but realistically, no one would come to an unprofitable newborn dungeon without a request.
And so, the two knights enjoyed the onsen.
The conclusion? It felt amazing.
The temperature of the water, the depth of the bath, they were just perfect.
Most natural onsens are either too hot or too cold, and their baths are usually too shallow or deep to be useful for humans.
But this place was perfect.
It felt like a natural onsen bathhouse managed by a professional merchant.
And what's more…
Their skin… felt incredibly smooth and beautiful.
…Or did it?
Was it just their imagination?
No.
The dry, rough patches of their skin were visibly moisturized.
The palms calloused from gripping swords too much, the cracked soles from excessive walking, they were all regaining something of a maiden's soft skin.
"Senpai… I think the acne on your face is reducing."
"You too… all those heat rashes under your armor have disappeared."
"…"
"…"
"Isn't this amazing?"
"Yeah… it might be incredible… We must report this to Her Majesty immediately."
"Ah… but let's stay in just a bit longer… just a little more."
"Ah… yeah… I can already see the future where it's so popular we can't get in anymore…"
With that, the two women kept pouring water over their faces and hair like mad, soaking for hours. Eventually, they became lightheaded and ended up passed out, naked, sprawled out on the cave floor. By the time they returned to the royal capital, the sun had long since set, and it was deep into the night.