Kawai Sakiho was a civil servant working at the Sugai Dungeon branch office.

Right after graduating high school, she had used her uncle’s connections—he worked at city hall—to get hired as a clerical worker. For her first two years, she worked at city hall without incident. In her third year, however, her uncle was exposed for embezzlement in the course of his duties, and as a result, she was transferred to what was considered a “dead-end” department among government offices: the Dungeon Division. To make matters worse, she was assigned to the branch office of the Sugai Dungeon—an already-cleared D-rank dungeon.

Frankly speaking, she had zero motivation.

Even so, there was still a minimal amount of work to be done, and Sakiho spent her days halfheartedly carrying out her duties while venting her complaints whenever she felt like it.

At one point, a proposal came up to recruit a “cleaner” for the Sugai Dungeon.

Even cleared dungeons could still function as hunting grounds depending on the monsters that spawned there, but the Sugai Dungeon offered no such appeal. The monsters had no value, and it wasn’t even suitable as practice for beginner explorers. If left unattended, it was obvious to anyone that a Dungeon Stampede would eventually occur.

Whether that would be in a year, five years, ten years, or even twenty—no one could say.

Humanity, having survived the world fusion of 1999 and the “Chain Stampede” of the early 2000s, feared dungeon stampedes above all else.

Until now, monster extermination duties had been assigned to former explorers employed by the Dungeon Division. However, the Sugai Dungeon was simply too insignificant. Sending division personnel there was, bluntly put, a waste.

One might ask why they didn’t just destroy the dungeon core at the deepest level and be done with such an unprofitable dungeon—but doing so was said to cause a new dungeon to appear somewhere else.

This theory hadn’t been fully proven due to a lack of research, but it had practically become accepted wisdom. During the disastrous Chain Stampede of the early 2000s, it was often said that “new dungeons appeared because explorers destroyed too many existing ones.” In some cases, nearby dungeons had allegedly mutated into far more dangerous forms.

Because of that, dungeons couldn’t be destroyed lightly.

The Sugai Dungeon had no upside, but it was easy to manage—or so it was regarded.

And so, people who couldn’t qualify as D-rank explorers were recruited instead.

In the context of Japan’s dungeon management, this was somewhat uncommon, though not unheard of. The “cleaner” position was a contracted job issued by the city, and the pay offered was so low that no legitimate explorer clan was expected to apply.

In fact, not a single registered explorer responded to the recruitment.

The one who raised his hand was a boy named Hayasaka Tooru—someone who had dropped out of high school at the time.

Having lost his family in the stampede of an undiscovered dungeon and left utterly alone in the world, Hayasaka Tooru had promptly dropped out of high school. At the time, he had been working multiple part-time jobs as a freeter. Apparently, the reason he applied for the cleaner position was that, since the city would be the contracting party, the benefits seemed reliable.

In other words, his social insurance and pension contributions would be automatically deducted from his pay.

For a seventeen-year-old high school dropout with no real social experience, he had thought things through reasonably well. Even so, Sakiho thought that if he were truly smart, he shouldn’t have dropped out of high school in the first place—and if he did drop out, he should at least have scraped together some money to take the high school equivalency exam.

Kawai Sakiho disliked Hayasaka Tooru.

She wasn’t sure exactly when she had become aware of it—probably quite early on.

He showed up at the branch office dressed like a construction worker, did nothing but hunt trash-tier monsters in the Sugai Dungeon day after day without complaint, and then came to the counter with an expression that looked neither particularly happy nor unhappy to submit the worthless-looking magic cores he had scraped together.

Honestly, even if he cut his workload to one-fifth, the amount paid out by the city probably wouldn’t have changed. All he really needed to do was perform cleaning duties in the upper layers of the Sugai Dungeon on a regular basis. The contract certainly didn’t say he had to work twenty days a month.

And yet, that boy was diligent.

Painfully, wastefully diligent.

Hayasaka Tooru was someone who couldn’t even become a D-rank explorer. In other words, he lacked talent—talent meaning the ability to adapt to the supernatural phenomena of the other world.

The aptitude known as mana affinity, the fundamental quality required of an explorer.

Most B-rank explorers were geniuses whose physical abilities skyrocketed after defeating just a single monster, and A-rank explorers were even more extreme, practically inhuman. Even when looking down at C and D ranks, they were still clearly different from ordinary people.

But Hayasaka Tooru was ordinary.

And the upper floors of the Sugai Dungeon were so easy that even an ordinary person could handle the cleaning work.

That was precisely why she hated him.

No matter how seriously he kept hunting monsters like that, it would never amount to anything.

Surely, even his former classmates had already cut ties with him. Working every single day like that, he couldn’t possibly have time to hang out. While he steadily ground his life down to nothing, his classmates would be enjoying their youth, moving on to higher education, savoring college life—and a lucky few would even ride the rails of what people called a “winning path.”

Hayasaka Tooru had no such rails.

And neither did Sakiho, who continued working as a dungeon branch office clerk out of sheer inertia.

◇◇◇

On that day, an A-rank explorer clan called Anthem was scheduled to enter a dungeon relatively close to the Sugai Dungeon, and Sakiho had been looking forward to it since morning.

Watching younger girls who possessed the kind of glittering talent she herself lacked—and who were letting that talent shine—was something she genuinely enjoyed. Anthem was an all-female explorer clan, after all, and admiring them from afar suited her just fine.

For someone with very few hobbies, getting hooked on watching their streams was a rare exception.

Apparently, there were women who felt jealous of them from time to time, but Sakiho thought that was simply stupid. Things that truly shone were meant to be admired from a distance, weren’t they?

So, as usual, she went to work, changed into her suit, boldly spread out her terminal at the reception desk that never saw any customers, and started watching Anthem’s live broadcast.

For this expedition, it seemed the team consisted of their leader Saitou Megumi, the healer and most idol-popular member Midou Airi, the samurai girl who wielded a blade, Kagurazaka Chizuru, and their dedicated cameraman—four people in total.

With three A-rank explorers, a B-rank dungeon was a breeze, and both before and after entering the labyrinth, the girls of Anthem looked like they were having fun.

Even the occasional monster that appeared was dispatched without the slightest hint of danger.

“Looks like this run won’t be your turn to shine,” Megumi said with a slightly mischievous grin, poking Airi in the side.

Airi smiled happily at that and nodded energetically.

“If I don’t have a turn, that’s better. As long as Megu-chan and Chizuru-chan don’t get hurt, I’m happy. So you two, don’t make a situation where I need to step in, okay?”

What a good girl, Sakiho thought.

She continued watching the stream without a hint of self-reflection, but about two hours after the broadcast began, the branch office’s automatic doors slid open.

A customer? In a place like this?

Annoyed at the interruption of her enjoyment, Sakiho selfishly cut the stream’s audio—but the moment she saw who had entered, she quickly put on her professional smile.

A weary middle-aged man in a suit—the section chief of the Dungeon Affairs Division, Sadoyama Kouji.

“Morning, Kawai-chan. I had something on my mind, so I thought I’d stop by.”

“Good morning. Something on your mind?”

Sakiho tilted her head slightly at Sadoyama, who stood outside the reception counter with a sloppy, almost customer-like grin.

Her days were always dull and unchanging, and as far as she was concerned, the only thing worth being curious about right now was Anthem, who were currently exploring the Kamioka Dungeon.

“Right, right. That thing that’s been bothering me. You know about it, don’t you? I’m sure you do, so I’ll talk on that assumption—an A-rank explorer clan has come into our jurisdiction.”

“Anthem, you mean?”

It was such a timely topic that Sakiho responded without thinking.

“Yeah, that all-girl clan—though calling them that might be a compliance violation these days. Ha! Must be nice, right? If it’s just girls getting together, they get praise and attention, but if it’s just men, suddenly it’s ‘excluding women.’ You’d never have imagined that back in the day.”

Muttering something like what a pain, Sadoyama leaned against the counter.

Sakiho, who had been born after the World Fusion and belonged to what people called the otherworld generation, couldn’t really grasp that mindset—but she didn’t care about the section chief’s ideology in the first place.

“So, what is it that’s bothering you?”

“Ah, yeah, that. Lately, we’ve been getting some strange reports from within our area. Multiple dungeons, all with similar accounts. People saying they hear something like a ringing in their ears.”

“I see…”

Sakiho nodded along, thinking she wished he’d just get this over with already. She was agreeing automatically, not really listening.

“Kawai-chan. Have there been any reports like that from the Sugai Dungeon?”

The way Sadoyama curved his lips into a smile and narrowed his eyes—his whole atmosphere changed.

The sloppy, harmless middle-aged man vanished, replaced by something sharper: the air of a site supervisor who didn’t tolerate mistakes, the kind of edge possessed by someone from the field rather than the office.

A former A-rank explorer letting a trace of pressure slip.

The slack, lazy mood from moments before disappeared completely. Sakiho flinched despite herself, her body tensing as she looked back at her superior. She looked back—before she could stop herself.

At least do the bare minimum.

That was what his gaze said.

Which meant… she hadn’t been doing the bare minimum?

No—she had submitted all the required paperwork properly. She had never neglected the formalities she was supposed to handle.

“The young cleaner—you know, that kid. Hayasaka-kun, was it?”

“Huh—?”

“Kawai-chan, you had a few run-ins with him, didn’t you? Saying the amount of magic cores he submitted was suspicious, suspecting illegal acquisition. After that, Hayasaka-kun started doing those dungeon cleaning streams as proof, didn’t he?”

“Ah…!”

Only then did Sakiho finally remember the report she had received from the cleaner the other day.

“Does something ring a bell?”

“Uh, um… I did receive a report from Hayasaka-san. He said he heard something like a ringing sound in his ears on the third-floor corridor of the Sugai Dungeon. He even gave the exact time in the stream, but…”

“You don’t remember?”

“…No.”

“So you figured it was probably nothing and sat on the report. Well, whatever. In any case, since he was kind enough to leave us video evidence, let’s take a look.”

Without scolding her for the obvious lapse, Sadoyama walked around to the staff side of the counter, booted up a management terminal that was rarely used, and connected to a streaming site.

What appeared on the monitor was a bland, no-frills channel titled Recorded Cleaning Stream. There wasn’t even a header image, and all the thumbnails were auto-generated, resulting in a monotonous lineup of near-identical images.

“The day that report came in?”

“The day before yesterday. He wrapped up earlier than usual that day, so…”

“Seems so. The stream’s shorter than usual. …Hmm? If we’re saying that, yesterday’s stream was short too… Well, let’s check the relevant one first. Oh—Hayasaka-kun’s left a comment on his own video. He’s even put in the timestamp and chaptered it.”

The way Sadoyama handled the terminal was remarkably smooth. He might regularly watch dungeon exploration streams—cleaning streams, in Hayasaka Tooru’s case.

“Well then, let’s have a look,” Sadoyama said—and clicked the play button.