Daedalus Street deserved its name as a labyrinth street. Even high-level adventurers who set out to memorize the way and walk it would still end up lost, so long as they left no marks and didn't follow the road markers.
Leo and the others went further and further into the out-of-the-way parts, and the roads they walked grew more complicated and drawn out, until eventually none of the four recognized the way, and they didn't even know where they were.
"I, I can't take any more..."
Line had started getting dizzy, with tears at the corners of her eyes, and the route map she'd been drawing had at some point turned into a tangled knot, which nearly made her cry.
"How can a road be this complicated? Even the Dungeon doesn't have a maze structure this complicated!"
Lefiya wailed as if she couldn't stand it.
Her words weren't quite right. Some of the Dungeon's labyrinth terrain really was complicated, especially the terrain past the Deep Floors, where the range grew wider and the area grew larger until it formed labyrinths of unimaginable complexity.
The reason Lefiya felt this place was more complicated than the Dungeon's labyrinths was, first, that the Dungeon's labyrinths had been explored by generations of adventurers, so that even if the terrain hadn't been fully mapped out, the main routes to the next floor had been felt out and detailed maps drawn, and adventurers who could reach those places usually didn't get lost. Second, they were newcomers here, exploring Daedalus Street for the first time, and deliberately heading into the out-of-the-way areas at that, which naturally made it hard to get their bearings.
If they had followed the markers from the start, the odds of getting lost would still have been low.
But there was no denying that Daedalus Street was hard to walk, and that they were lost now.
Even Ais turned a look at Leo that asked for rescue, silently asking him what they should do next.
"It's fine, let's keep going. We'll pick the out-of-the-way places on purpose, and it doesn't matter if we get lost." Leo said, reassuring them, "This is the surface after all, and the sky is right over our heads. Worst case I use flight magic and carry you all out. There's no way we'll be trapped in here."
Everyone was startled for a moment, then found that he had a point.
This was the surface after all, and for Leo, who could fly, there was no way he couldn't fly out.
As long as he could get into the sky, no matter how complicated the terrain, it was useless. Leo could just fly toward the city's main district, or even toward Babel towering up into the clouds, and that would do it.
With that to fall back on, no one worried about getting lost anymore, and just as Leo said, they picked the out-of-the-way places on purpose, determined to turn up some trace of a clue.
Leo walked at the front, his eyes sweeping the surroundings the whole time.
He was looking for a way into the underground waterways.
Others didn't know, but Leo knew perfectly well that the destination they were searching for this time was in the underground waterways.
So he wasn't wandering at random at all. He was guiding them with a purpose.
After walking like that for a while, Leo finally spotted an entrance to the underground waterways set in a corner at the foot of a stone wall, closed off by an iron grate door.
"Come on." Leo didn't hesitate. "Let's go look in the underground waterways."
"The underground waterways?" The others were slightly taken aback, and Line spoke up in surprise. "Mr. Leo suspects the bad guys are hiding in the underground waterways?"
To that question, Leo only gave one reply.
"It suits them, doesn't it?"
With that, Leo stepped forward to the iron grate door.
He glanced at the lock on the grate door. The lock was covered in rust and clearly had some years on it.
Leo just gripped the lock and gave it a light twist, snapping it easily with his Lv.6 Status.
He opened the grate door, and a spiral staircase leading underground appeared in front of them.
Leo walked in, and the girls exchanged a look and walked in as well.
None of them thought there was anything to hesitate about in going down into the underground waterways.
They could walk down into a place like the Dungeon without changing expression, so what was a mere underground waterway?
Filthy? Chaotic? Foul-smelling? Grim?
Environments far worse than that were everywhere in the Dungeon.
So neither Ais, with a face as beautiful as a goddess's, nor Lefiya, an Elf who liked things clean, flinched at going into the underground waterways.
Line even took a portable magic-stone lamp out of her bag and flicked the switch, letting it give off light and push back the darkness.
The four of them descended the stairs the whole way, walking for quite a while before they arrived in the dim sewer.
Small magic-stone lamps near the end of their lifespan were set into the walls here, with walkways for people on the left and right and the waterway itself down the middle, from which the sound of flowing water came clearly.
Looking closely, the whole underground waterway was a tubular tunnel built entirely of stone, about six meters in diameter. Leo and the others were currently on the narrow walkway on the right side of the sewer, and they could faintly see branch waterways converging in from various places, making the sound of water echo in layers through the sewer.
"...It's unexpectedly clean in here."
Lefiya had prepared herself mentally for a filthy environment, only to find the situation better than she'd imagined.
At least there was no grime and garbage lying around everywhere, and while the air was murkier than above ground, there was no stench that made you want to pinch your nose. The water flowing in the waterway wasn't the sewage they'd all imagined either, and looked much like ordinary water.
"Is it because of those purification devices?"
Line looked at the several crystal pillars set in the trench of a long, narrow branch waterway.
They were crystal pillars giving off a blue-purple glow, shaped like iron railings.
Every adventurer was familiar with that glow. It was the glow given off only by the magic stones dropped from monsters in the Dungeon.
Those crystal pillars were clearly a magic stone product, and their function was to purify the sewage that passed through.
The purification pillars, lined up at even intervals like a fence, purified the sewage flowing past and turned it into clean, clear water, which was why the water in the trench was transparent and clear, not at all like sewage discharged from the city district, and why the sewer wasn't reeking to high heaven.
"Let's go."
Leo called to the girls and started forward through the sewer.
There were countless lateral passages and staircases opening in the walls here, plus bridges spanning the trench, so walking through it really did have something of the flavor of the Dungeon, as if they were exploring inside it.
They had no clear destination either, and just walked by the same principle as before, choosing the out-of-the-way roads and looking carefully to see whether there were signs of people active here.
In the end, they hadn't yet found signs of people, but signs of monsters turned up.
Some fish monsters, led by a type called the ambush fish, attacked out of the water, startling both Lefiya and Line.
"Wait... why are there monsters here?"
Lefiya hurriedly knocked an ambush fish flying with the staff in her hand and spoke with a certain amount of fluster.
"Did they swim in from the rivers outside?"
Line hid behind Leo, but she guessed where these monsters had come from right away.
The wastewater in Orario's underground waterways was eventually discharged into the rivers that flowed near the city, then into the nearest brackish lake, called Lake Lolog. That brackish lake also connected to the sea, so it wasn't hard to understand that some aquatic monsters often came up from the sea against the current, reached Lake Lolog, then reached the nearby rivers, and finally swam into the city sewers connected to them.
As for why there were monsters outside at all, that had to be traced back to the ancient period before Orario was built.
Back then, monsters pouring out of the Dungeon spread across the entire lower world, and although they were eventually driven back into the Dungeon through the efforts of the ancient heroes and sealed in by Babel and the fortress city, it was impossible that none of the monsters spread across the whole lower world at that time had slipped through the net.
Those that slipped through the net had long since bred on the surface over the long years, so monsters did appear on the surface outside as well. It was only that after generations of breeding, the power in their magic stones grew less with each generation, so monsters outside were generally much weaker than monsters of the same type in the Dungeon.
With the exception, of course, of the three monster kings designated by the Three Great Quests that threatened the entire lower world.
Those three monster kings had survived from ancient times into the modern age, threatening the peace of the whole lower world all along, until fifteen years ago when Zeus Familia and Hera Familia moved and subjugated two of the three monster kings, and the threat to the lower world was reduced. Unfortunately, they fell under the claws of the last and strongest monster king, the One-Eyed Black Dragon.
What Leo and the others had run into now were monsters bred outside, which had come into the city sewers through the connected rivers and were leaping out of the current to attack one after another, but they were considerably weaker than monsters of the same type born in the Dungeon.
So after the initial panic, everyone came to their senses and organized a counterattack.
Ais only swung her sword lightly a few times, and the sword light cut apart several of the ambush fish that came flying at her with no effort at all, scattering their blood through the air.
Lefiya knocked away the ambush fish that flew at her one by one as well, resolving these monster fish without even using magic.
In the Dungeon, ambush fish were monsters of floors 25 to 27, that is, monsters of the Water City connected by its magnificent great waterfalls.
Floors 25 to 27 were part of the Lower Floors, and by the Guild's recommended difficulty guidance, they were floors where only Lv.3 second-class adventurers could tackle them in relative safety.
In other words, a Lv.3 second-class adventurer generally had the ability to handle the monsters of floors 25 to 27.
Lefiya was a Mage and not good at close combat, but she was already Lv.4, and these ambush fish were weaker than monsters of the same type in the Dungeon, so even without using magic, with her current Status she could knock these ambush monsters flying.
Under these conditions, Leo couldn't be bothered to lift a hand, leaving the monsters to Ais and Lefiya while he took charge of protecting Line and scouting the route.
Walking on like that, after who knew how long, an iron door appeared in front of Leo and the others.
"This is..."
Leo narrowed his eyes slightly and stepped up at once to examine it.
It was an old double door from a long time ago, fitted with a large lock that had real weight to it, sealing the two door panels tightly shut.
"Line, come take a look at this door."
Leo had found a metal plate mounted on the wall with faint characters that could just barely be made out, so he called over Line, who handled the support work.
"Okay." Line came up and looked it over, then said, "This looks like an old-style waterway door, a model that was abandoned and stopped being used a long time ago."
"An abandoned door?" Lefiya came up too and said in surprise, "Then does that mean the passage behind this door is abandoned as well?"
Leo was still examining the door when Ais, standing beside him, spoke.
"This door has marks of recent use."
Ais speaking up startled everyone, and then they noticed the problem too.
"She's right, the lock has clear marks of being opened and locked again many times."
Line checked the lock and came to that conclusion.
Everyone looked at one another, and each saw the same thought in the others' eyes.
That was, they might have found their target.
After all, an abandoned door, in a place like the underground waterways, and yet someone was using it over and over. Wasn't that enough to show that someone was active around here?
And who would run around in the underground waterways with nothing better to do?
"Come on, let's go in and look."
Leo didn't hesitate. He crushed the lock, pushed the door open, and let the old waterway behind it come into everyone's view.
Magic-stone lamps were installed high on the walls of this old waterway, glowing with points of pale light, but the steps in front of the door, the passage, and the waterway were all under water, rippling black like a river at midnight.
"The water doesn't seem deep."
Lefiya tested the depth with her staff and found it was about as deep as a shallow shoal, with the waterline reaching her calf at most.
"I'll go down first."
Leo glanced at the girls with him and noticed they were all wearing skirts, so entering the water would at most soak their shoes, not their clothes.
He, on the other hand, was wearing long trousers, plus the hooded cloak of the Giant's Battle Garb, which would probably get soaked.
Leo sighed, took off the cloak and handed it to Line, having her stuff it into the shoulder bag she carried, and then walked into the water.
The splashing of Ais, Lefiya, and Line entering the water came from behind Leo.
Leo didn't look back. He held up the magic-stone lamp he'd taken back from Line and waded forward the whole way.
The waterways here criss-crossed, more complicated than the sewer they'd been in before, with more of a labyrinth flavor.
After wading through the water like that for who knew how long, Ais spoke again.
"...They're coming."
The girl's terse voice was full of a chill, and it came with the sound of a sword being drawn.
Leo, Lefiya, and Line all tensed, knowing exactly what those words of Ais's meant.
The female swordsman with her sharp perception of monsters would react like that for only one reason.
That was, monsters were about to appear.
And they were the monsters the group was looking for.
In the passage ahead, something huge broke the surface of the water.
Violas with yellow-green skin twisted their long, thick bodies and appeared, tangled together.
"Ohhhhhhhhhh...!"
That familiar cracked-gong roar made one thing clear to them.
They had found the right place.
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