"The sound of water is coming through. It feels like the humidity has risen slightly."

The staircase was just as long as the one leading to the third layer.

Just like when I saw the third layer, it's hard to believe there's such a space deep underground.

After a while, the stairs ended.

Dodo-dodo-dodo—explosive sounds echoed through the air.

The ground was soaked with water droplets, the air thick with moisture, and simply standing there made my clothes damp.

"……It's an incredible sight. It's almost a shame only explorers get to see this."

What lay beyond the stairs was, indeed, a massive waterfall resembling a dragon coiling upward.

I was likely at about mid-height of the waterfall.

The water seemed to come from a very high point, perhaps from an underground watercourse.

I did take a look at the four-layer map, but since it's a three-dimensional structure, it wasn't easy to grasp from the map alone. Indeed, one would have to walk through it in person to truly understand.

"It looks like it's about 100 meters high. If you fell into the pool at the bottom, you wouldn't survive."

Even as I speak, I'm unsure whether the audience can hear me over the deafening roar of the waterfall.

From my position, I can't see the pool below, and there's no safety barrier, no anti-slip measures, nor any ropes stretched across.

It's a dangerously slippery slope—just one misstep and you'd be plunging straight in.

"I can now understand why the fourth layer is considered too dangerous for exploration. The thunderous noise could easily mask the presence of monsters."

In reality, in a quiet space, even small sounds like footsteps or breath can reveal a lot of information.

If the sound of the waterfall drowns it out, the element of surprise becomes significantly greater.

"I'll begin the exploration now... ah, before that, let me try out a new technique."

Kage no Mi had advanced to Rank Three, unlocking a new ability.

"The 'Night Vision' ability has evolved into 'Dark Sense.' Let me test it out."

Current proficiency level is as follows.

【Shadow Spirit Arts】

Second Rank Techniques

・Shade Void 【Shade Shift】 Proficiency 4

・Shade Coffin 【Shadow Bind】 Proficiency 74

・Shade Call 【Summon Night Bug】 Proficiency 69

Third Rank Techniques

・Shade Sight 【Dark Sense】 Proficiency 0

・Shade Transformation 【Phantom Warrior】 Proficiency 6

・Shadows Storage [Shadow Storage] Mastery Level 5

Fourth Rank Spell

・Shadow Manifestation [Darkness Fog] Mastery Level 88

Special Spell

・Shadow Return [Create Undead] Mastery Level 1

Finally, the first rank has disappeared. One could say it's progressing steadily.

Personally, I'm looking forward to seeing Nightbug advance to the next level. It's the only offensive spell.

That said, judging by how often it's used, Nightbug is among the harder ones to level up. If things continue this way, Bind will likely reach the third rank before Nightbug does.

"Then, let's go. Dark Sense!"

The moment I activated the spell, I felt a wave of perception spreading out like a radar scanning through darkness.

The fourth layer is significantly darker than the third. Perhaps somewhere around midway between the first and second layers.

It was an odd sensation.

My perception spread out into the darkness within visual range, allowing me to sense not only the terrain but even whether monsters were hiding within it.

If Night Vision was the ability to see in the dark, then Dark Sense was the ability to detect what lay within the darkness. The two were similar yet quite different.

The ability to actively locate things was a major advantage.

Moreover, its range was extensive—capable of scanning up to about a hundred meters.

Since perception radiated outward in a spherical pattern centered on myself, it allowed for three-dimensional detection, which was a significant benefit. With this, I could even spot things hidden underwater.

As I walked toward the monster I had detected with Dark Sense, I explained it aloud.

Inside a cave that felt like a damp, rough stone surface, uneven walls and ceilings created plenty of hiding spots for monsters.

And it was a monster whose shape made it hard to spot, even when you knew it was there.

"There it is—a slime. It's clinging to the wall, just one of them."

It was about twenty meters away.

Whether it had noticed us was unclear, but its semi-transparent form, half-blended with the rock, made it easy to overlook.

"Summon Nightbug."

The Nightbug was an attack technique with a long range.

After all, it was a bug, so it was only natural.

Summoned shadow insects buzzed loudly and simultaneously charged toward the slime.

The slime's attack methods appear to be either dissolving its target by wrapping around it or suffocating it, but it's ineffective against opponents whose form is unclear—like dark insects.

Having its vital core gnawed by insects, the slime transformed into a spirit stone within seconds.

It would be troublesome if one didn't know about it, but once spotted beforehand, it seems manageable.

"We've successfully defeated it. Indeed, the importance of a preemptive strike is clear. The Dark Sense should prove useful on the fourth floor. Its effective range is around 100 meters."

Similarly, the second floor, though dark, is a structure that feels entirely artificial—floor, walls, and ceiling all made of stone. So on corridors, one only needed to watch out for what was in front and behind. But the fourth floor won't be that simple.

I can understand why Reflair dislikes the fourth floor.

"Then, I'll try exploring a bit. I've checked the map of the fourth floor, but since it's a three-dimensional layout, it didn't help much, so I'll have to feel my way around.

While giving a somewhat awkward, unclear commentary that's hard to tell if it's meaningful, I keep stepping away from the stairs to examine the terrain, then returning.

Things like how monsters appear, what kind of perception they have, or how fast they attack—none of that can be fully grasped from written information.

In the end, there's no substitute for learning through firsthand experience.

Last time, I had prior info saying the third floor wasn't too difficult, so I could afford to take some risks. But doing that on the fourth floor would truly be fatal. It might not be very entertaining for viewers, but this is all I can do.

"Dark Sense"

After walking for a while, I detect a monster beyond visual range using Dark Sense.

I'm using Darkness Fog as well, so the chance of being suddenly attacked is low, but I can't afford to be careless. There are no scouts, and since this is the first floor, I won't hold back on using my techniques.

"There are two Giant Claws deeper inside. They're larger than I expected."

Thanks to Dark Sense, I can perceive the monsters even without seeing them—knowing their shape through sensation alone is incredibly useful.

Giant Claws are large crabs, equipped with massive pincers capable of slicing a human in half, and covered in thick, hard shells. This one seems like a particularly ill-fitting opponent for me.

Above all, they're huge—though saying they're the size of a compact car might be stretching it, they feel nearly that big in person.

I could probably handle them if I had a giant weapon like Refraya, but fighting them with ordinary gear would be extremely tough.

Incidentally, I’ve already investigated the vital point—the weak spot—within the guild, and the target’s weakness lies between its eyes.

"Honestly, fighting two Giant Clubs with just my own strength is tough… but I can’t back down here. I’ll do it."

Drawing my short sword from my waist, I mentally rehearse how to fight.

Relying on dark spirit magic could easily lead to a disastrous outcome from a single unexpected twist. Especially when I’m alone—no one’s coming to help.

Yet—no, precisely because of that—I have to go through with it.

To gain more viewers than ever before, I must create a situation where the audience truly believes, “He’s gonna die.”

I don’t have any other way to achieve this.