The Sugai Dungeon was originally supposed to spawn nothing stronger than D-rank to lower C-rank monsters. And yet by the twelfth underground floor, it had transformed into a demonic den where even upper B-rank monsters appeared.

That said, the terrain itself had not changed.

The structure of the labyrinth remained intact—only the monsters that appeared had shifted.

“You can’t call this D-rank anymore, not even as a joke.”
“You’d almost forget how dangerous it is since they are moving through without a hitch, but this place is seriously deadly now.”
“The published map goes down to the fifteenth floor, right?”
“No. The sixteenth floor was the deepest boss room. It was supposed to be a fully cleared dungeon.”

“Ahh… you guys are seriously knowledgeable. You know way too much.”

As he made his way along the twelfth-floor corridor, Tooru checked the livestream chat and let out an honest note of admiration.

“It’s just that you surprisingly don’t know much, Tooru-bro.”
“Well, as long as he’s working as a cleaner, he doesn’t need info about the lower floors anyway.”

“Hey, hey—are dungeons like this common? You know, not that complicated in layout, but the monsters just keep getting stronger and stronger. Normally, wouldn’t the difficulty of a dungeon include how hard it is to find the next staircase?”

Still not wearing armor as usual, Tia strolled along leisurely with the holy sword in one hand as she spoke. Of course, she wasn’t directing the question at Tooru. It was likely meant for Kujou Reiko, her butler Kashizaki Jouichirou, and the viewers.

“Well,” Reiko replied, “generally speaking, a dungeon’s difficulty and the rank of its monsters tend to rise in tandem. However, there are rare cases where the maze, mechanisms, or riddles are extremely difficult while the monsters themselves are only moderate in rank—and the opposite also exists.”

“I see. In dungeons like that, do they usually have treasure chests or relics? I mean, those would be the main attraction rather than monster drops, right?”

“That is what they say. I have never attempted such a dungeon myself, so I cannot speak in detail…”

“M’lady has zero interest in puzzles.”
“She specializes in fighting monsters, after all.”
“Treasure from riddle dungeons? M’lady doesn’t need that lol.”

“Everyone has their own field of expertise! When one speaks of dungeons, one speaks of monsters! One defeats them with one’s own hands! One obtains magic cores and rare drops, and returns them to society! That is the standard of an explorer! Ohohohoho!”

Her loud laughter rang clearly through the stone labyrinth.

Judging from the livestream chat, however, Kujou Reiko’s claim did not appear to be quite as “standard” as she insisted. In the first place, explorers who entered dungeons in pairs and focused primarily on combat were apparently the rarer breed.

“Yeah, I doubt we’d have much business in a puzzle-type dungeon anyway. Honestly, I’m terrible at riddles, and Tooru would probably just get annoyed with all the hassle,” Tia said.

“Really? Bro-san doesn’t seem stupid or anything.”

The butler handling the camera said it in a perfectly normal tone. It wasn’t praise, nor was it an insult—just a straightforward observation.

“Mm, but Tooru’s lazy, right? He was already grumbling about setting up the streaming equipment. If there were a door that only opened after solving a riddle, wouldn’t he just cut it down with the cursed sword?”

“I wouldn’t. Not unless I had to.”

“So you would if it was necessary? lol”
“Yeah, Tooru-bro totally would.”
“Most people don’t jump straight to ‘cut the dungeon wall down.’”

“Well, if there’s a dying kid behind the door, I’m not going to waste time solving some riddle. A treasure chest? Sure, I’d give up on that.”

“Mm-hm. That’s what I like about you, Tooru.”

“I find that part of you slightly irritating, though.”

“Eh!? That’s awful! I was just showing affection!”

“lmao”
“Shocked Tia-tan is cute too.”
“Fair enough.”
“Hmm, I’d call that even.”
“Eight to two, maybe lol.”

“By the way, Bro-san, Tia-san—if you add up the numbers from one to a hundred in order, can you tell me the answer right away?”

“Huh? Ahaha… stuff like that is a bit beyond me…”

“Five thousand fifty. You get fifty pairs that add up to a hundred and one. Saw it in some video.”

“What possible use is that!?”

“You get to show off in moments like this.”

“lmao”
“True.”
“Tooru-bro’s not as much of a musclehead as M’lady, huh lol.”

While they were going back and forth like that, a monster’s presence stirred from the far end of the corridor.

Though they had never formally agreed on it, things had naturally fallen into a rhythm where Kujou Reiko and Tooru took turns handling combat. This time, it was Tooru’s turn.

From the darkness emerged a bear wrapped in golden fur, roughly two meters in length. Whether that made it bigger or smaller than a real bear, Tooru honestly couldn’t say.

“It’s an Old Bar!”

“That’s an upper B-rank Gold Bear. The rare drop, Kumanoi Potion, is seriously profitable. Supply’s low, and Gold Bears themselves don’t show up that often.”

“The butler completely ignoring M’lady is killing me.”
“She’s still getting it wrong?”
“He corrected it to Gold Bear once before!”
“‘Profit gang is wise.”¹
“She probably thinks ‘Toorubro’ is Tooru-bro’s actual name too.”
“You might not have noticed, but your channel just passed thirty thousand subscribers.”
“Viewers are over forty thousand too.”
“Congrats!”
“That’s insane! Probably the fastest among dungeon streamers!”
“Well, the channel itself’s been around for a while, so maybe not fastest.”
“Still amazing, Tooru-bro!”
“Congrats!”
“Congratulations!”

“Ah… well, I don’t really get all that stuff, but thanks for the subs and the comments. Anyway, I’ll be right back.”

A lot of coincidences had lined up to bring him here, but realizing that over forty thousand people were actually watching his stream stirred something in him after all.

It was a little embarrassing, though. So after offering his thanks, he quickly hoisted his iron rebar club onto his shoulder and walked forward to face the Gold Bear.

The warm look in Tia’s eyes—and her faintly indulgent smile—was probably not his imagination.

◇◇◇

An upper B-rank monster—if you compared it to modern weaponry from the previous century, it might be like facing an armored vehicle. Tooru had never fought an armored vehicle, so he couldn’t say for sure, but the Gold Bear’s offensive power and speed far surpassed the common sense of any wild animal on Earth.

Bears, to begin with, possessed enough mass and toughness that if one collided head-on with a small truck, the truck would lose. A monster modeled after such a creature was, needless to say, even more troublesome. A casually swung foreleg could probably smash a concrete wall like tofu, and the speed at which it kicked off the ground and closed distance rivaled a fired crossbow bolt.

Fighting something like this one-on-one was absurd.

Thinking that, Tooru sidestepped the Gold Bear’s ludicrous right-arm swipe as it charged him. Spinning smoothly with the motion, he brought his iron rebar club around and slammed it into the back of its head. Ordinarily, such a blow wouldn’t faze a bear—but this strike was infused with mana. What should have been a simple impact hit like a direct strike from a pile driver.

With Tooru’s current mana capacity, such a blow should have been impossible.

The explanation was simple.

He minimized the mana invested in each motion and concentrated it solely at the instant of impact. Of course, for a novice explorer, such precision control would be unthinkable.

The cursed sword devouring half of Tooru’s soul was automatically optimizing his movements—including his mana flow.

Evade.

Preparation.

Swing.

Impact.

If each action consumed ten units of mana, the sequence would cost forty. But if three units were enough to dodge, seven remained. The preparatory motion required none. There was a limit to swing speed, and if mana could be concentrated only at the moment of impact, a ten-unit strike could be amplified to thirty. The more finely each motion was divided, the more mana could be conserved. Of course, it still had to be used where necessary.

To damage a monster, an attack infused with mana was required.

Therefore, mana was stripped away from everything else.

That pattern of movement had been installed into Tooru’s body.

Struck in the back of the head, the golden bear pitched forward from the force and rolled across the dungeon floor. It had already been charging toward Tooru, which only made it worse. Before the bear could push itself back up, Tooru’s next move was faster.

He closed the distance in a flash, aimed for the ear canal, and drove the iron rebar club in. The moment it penetrated deep enough, he kicked the protruding end.

The dungeon gear—combat boots funded by Kujou Reiko—were reinforced like safety boots, steel cores embedded in the toes—likely something even sturdier. Kicking the rebar wouldn’t damage them.

With a wet, crushing sound—the Gold Bear’s skull split.

Of course, he did not let his guard down.

Even if he could fight it, taking a direct hit from an upper B-rank monster with his current total mana reserves would be disastrous. The instant his attack concluded, he was already well outside the reach of the bear’s forelegs.

Keeping wary of ambushes from the surroundings, he rested the club on his shoulder and watched as the Gold Bear dissolved into particles of mana and vanished.

He stepped forward to retrieve the magic core it had dropped—and noticed a strange little vial lying beside it.

“Jackpot, indeed! The Kumanoi Potion!² What extraordinary luck, Toorubro-sama!”

Still not used to Kujou Reiko’s booming declarations of joy, Tooru flinched slightly before picking up the small vial rolling on the ground.

He could more or less understand why a magic core—the crystallization of mana—would drop. But a transparent vial filled with liquid appearing like this? That part made considerably less sense.

“First rare drop of the run!”
“More importantly, he’s fighting way too cleanly.”
“Taking down an upper B-rank Gold Bear with bundled rebar is insane.”
“The attacks are brutal. Jamming rebar into its ear lol.”

After slipping the vial into his magic bag, Tooru glanced at Tia’s mobile terminal to check the chat. They were certainly having their say.

“Uh… well, my gut feeling is that if I stood there trading blows head-on, I’d probably struggle against a mid-C-rank or so. But there’s no reason to trade punches. You just dodge and land your hits, right? And instead of hitting the stomach, you go for the head. Better yet, stab the eyes. That’s kinda how I see it.”

“That’s asking the impossible.”
“Brutal lol.”
“Wanna hear Tia-tan and M’lady’s take too.”

“So they say.”

“Hm? Oh—well, let me see. The amount of mana I sense from Toorubro-sama at close range is not particularly large. I would place him somewhere between mid and upper C-rank explorers. I fully intended to step in at once if I sensed danger, yet he shows none whatsoever.”

Reiko had hesitated for a moment before answering. She had apparently been replaying Tooru’s earlier fight in her mind—smiling to herself as she lightly stepped and threw shadowboxing jabs, simulating how she would have handled the Gold Bear’s charge.

“I think he can push a bit further. Even if he gets hurt, I can use healing magic. And if things get dangerous, I’ll just step in,” Tia added.

“Is this a gathering of battle junkies or what?”

“Bro-san, Bro-san—I’m not part of that group, okay?”

The butler sided with him as though it were someone else’s problem entirely. Since he sounded exactly like it was someone else’s problem, it wasn’t particularly reassuring.

That said, Tooru had no intention of overreaching if things truly became impossible. The troublesome part was that, at least for now, he could honestly say it wasn’t impossible.

“Oh—right. I accidentally tossed it into my bag.”

Remembering, he retrieved the Kumanoi Potion—the Gold Bear’s rare drop—from his magic bag. After a moment’s hesitation, he handed it to Jouichirou.

“The Kumanoi Potion is a panacea effective against most illnesses. On the open market, it would fetch at least one hundred million yen. The options would be to secure it for research, submit it to the Dungeon Agency, or place it at auction. Should it be for research purposes, the Kujou family would be delighted to purchase it,” Reiko explained.

“Huh? When we saved the Anthem people, wasn’t the dragon’s rare drop worth less than this potion?”

Tia tilted her head in genuine puzzlement. Even Tooru could vaguely understand this one. As a general rule, the market decided the value of things.

“Isn’t it just because the only people who want dragon scales are explorers? I don’t know the details, but I’m pretty sure rare materials like that aren’t allowed to be freely traded.”

“Freely traded?”

“Uh… what was it again? I saw something on the news once—if dungeon-produced materials are allowed to circulate completely unchecked, it can get pretty bad.”

Tooru wasn’t well-versed in economics, so it was hazy recollection at best. But after surviving the chaos that followed the World Fusion, there had been talk of parts of Europe where dungeon materials brought back by explorers had become so overvalued that it led to worsening public order and even infrastructure collapse.

“Most likely,” Reiko said, “materials of that level are classified as non-purchasable and are taken in by the Dungeon Agency for a token sum. In practical terms, the money you received for defeating that dragon and the Black Knight would have come primarily from the magic cores.”

“Huh… wouldn’t adventurers— I mean, explorers—complain about that?”

“They do, on occasion. However, as a matter of convention, explorers who submit such ‘Special-Class’ materials are provided with equipment by the Dungeon Agency. Moreover, a certain degree of ‘restriction’ on exploration activities is justified under the pretext of maintaining social stability. If one cannot agree to that, one is simply advised not to become an explorer.”

On that point, Tooru couldn’t entirely disagree.

He had no illusions that the system was perfectly fair or just in every detail. Even so, the fact that society had managed to function at all while accommodating such alien elements as dungeons, dungeon products, and explorers was borderline miraculous.

After all, it had only been twenty-five years. Five of those had been nothing but chaos. And these incomprehensible things called dungeons kept disgorging materials and phenomena with no regard for reason or balance. In that context, if explorers had to shoulder a little of the burden, perhaps that was inevitable.

“That level of material is insanely rare anyway.”
“We don’t know how much he made from Anthem, but letting the market run wild already backfired in parts of Scandinavia.”
“And you can’t exactly smuggle that stuff overseas because of the restrictions.”

“So… letting ultra-rare materials leave the country wouldn’t benefit domestic explorers. And by extension, it wouldn’t benefit national interests. Something like that?”

“Yes, that is the essence of it. There are several other reasons as well.”

How perceptive you are, Kujou Reiko added as she smiled. Tooru, who had almost no experience being praised like that, found himself completely at a loss for how to respond.

“A panacea, huh. So it’s less rare than dragon scales, which means it actually circulates on the market instead. Even then, there are still restrictions, right?”

“Indeed. If the Kujou family were to purchase it as research material, we would offer one hundred million—even after deducting the tax imposed on dungeon-produced goods. If you were to place it at auction, it would likely fetch somewhere between one hundred million and three hundred million. In some cases, it might even surge to five or six hundred million. However, as you noted, dungeon-related auctions are subject to certain restrictions, so prices do not spiral upward without limit.”

“Yeah… if some ultra-rich tycoon just scooped up everything, that’d get ugly fast.”

Ordinarily, that would simply be market principles at work. But when it came to dungeon-related items, leaving things entirely to market forces would likely cause something to collapse.

Tooru didn’t know the finer details, but perhaps there were limits on which powerful magnates could even enter such auctions.

“Of course, if you choose the auction route, you would receive the final price minus listing fees and tax. However, it would require some time. Which do you prefer?”

“Research.”

He didn’t need to think about it.

If the choice had been between ten thousand and fifty thousand, maybe he would have hesitated. But whether it was one hundred million or five hundred million yen, the scale of it was beyond his sense of reality.

In that case, there was no need for him to go out of his way to delight some dying billionaire. If not him, someone else would supply it eventually. But the number of people willing to let it go cheaply for research purposes? That was probably far smaller.

“Instant answer lol.”
“Not something most people could do.”
“Tooru-bro’s a good guy…”

“Hey, don’t go deciding whether someone’s good or bad over something like this. If I were on the rich side of things, I might’ve sold it at a high price to a wealthy acquaintance.”

“Mm-hm. I like that about you, Tooru.”

“Agh… yeah, yeah. Sure.”

“Hey, Tooru! Don’t brush me off! I think it’s terrible not to respond properly when someone says something like that!”

“Ohohoho! Toorubro-sama is simply shy, is he not?”

◇◇◇

Floor Thirteen

At the bottom of the stairs lay a straight corridor.

At the end of it stood a door.

Naturally, this did not match the existing maps.

The original thirteenth floor had been another maze-like layer, similar to those above. This was a different kind of anomaly—not merely “the structure is the same but the monsters have changed,” but a clear alteration to the dungeon itself.

“Toorubro-sama. Most likely… this is a boss room.”

Kujou Reiko said it with the corners of her lips curling upward.

Even the dullest observer would have noticed the delight radiating from her. It was the pure, almost innocent joy of a kindergarten child on a Sunday morning.

“This is it! This is M’lady!”
“Don’t bother trying to stop her, Tooru-bro.”

“I mean, I don’t really have a reason to stop her… but if upper B-rank monsters showed up on the previous floor, can you guess what’s in the boss room ahead?”

He tossed the question toward the viewers.

Several theories came in.

In a normal dungeon, it would naturally escalate to A-rank. Since it was a boss room, perhaps even mid A-rank. If the difficulty curve was gentler, it could be an enhanced upper B-rank variant.

And considering how Anthem had nearly been wiped out in the Kamioka Dungeon, there was even the possibility of an S-rank appearing.

“Well, if it gets dangerous, I’ll protect you.”

Tia said it lightly, without a trace of tension.

But Tooru had already decided yesterday that he would not rely on Tia’s version of “protect.” He glanced instead at the butler, who still held the streaming camera. Receiving a small nod in return, Tooru gave a faint shrug.

“Alright, let’s go. Before Kujou-san starts charging in.”

“O-ho-ho-ho! How prudent of you, Toorubro-sama! I was just about to dash forward in ten seconds! Of course, I jest! Ohoho! In a dungeon, vigilance upon vigilance is paramount! Everyone, your equipment checks are complete, I trust?”

“Oh—then I guess I’ll put my armor on, just in case.”

Tia said it with the same casual tone someone might use when deciding to toss a folding umbrella into their bag.

She vanished.

A moment later she manifested again in light armor, nudging the holy sword up with the tip of her foot before it could clatter to the floor. Catching it neatly, she turned toward the camera and gave a bright smile.

“Too cute lol.”
“Beautiful and cute? That’s unfair.”
“Tooru-bro, I envy you more about Tia-tan than the holy sword or the cursed sword.”

While he was skimming through those comments, ten seconds must have passed.

Kujou Reiko struck her gauntleted fists together with a sharp clang.

“—Now then, we proceed!”

1. This is an impossible 2chan meme to translate so I’m not even gonna try, but it’s about the way Jouichirou reads the word 旨味 (meaning good flavor, but has a billion figurative meanings like the ‘profitable’ here), which is normally read as ‘umami’ but uncommonly read as ‘uma-aji’. TL;DR is that some gay porn video posted there (yes they post a lot of gay porn memes there) used this word in the title (Uma-aji Gentleman) and as it was read ‘uma-aji’ it started sort of a flame war there between ‘umami’ gang and ‘uma-aji’ gang. This ‘uma-aji gang are smart’ phrase came around later on in reference to that ‘incident’. Writing all this down killed my last few brain cells but oh well.
2. Kumanoi means bear’s gall/bile. It’s been used as traditional stomach medicine especially in China. It’s written as katakana here as a name (proper noun) so leaving it as is.