In an instant, Tooru felt as though the world had been swapped out.

Just a moment earlier, they had been taking a break in the boss room on the fourteenth floor of the Kamioka Dungeon. It had been one of those moments where they planned to rest a little longer, then resume the stream.

That should have been the case—yet for some reason, they were now beneath a night sky.

Underfoot was dirt and grass. A perfectly flat stretch of ground, as if it had been leveled but someone had forgotten to lay down any asphalt or concrete. The chill of the night air. The sound of insects echoing from somewhere nearby.

In other words, they were outside.

It made no sense whatsoever.

When Tooru looked around, the other members of Anthem wore the same expression he did: This makes absolutely no sense. Even Irselia the elf was unable to hide her confusion and agitation. The only exception was Shinguu Sanagi, the camera operator. She was steadily moving the camera she held, panning around and filming their surroundings. Tooru found himself a little impressed by that dedication to filming—but… this really wasn’t the time for that… or was it? Maybe it was? He couldn’t tell.

Startled, he glanced down at the mobile terminal he had been absentmindedly holding, the stream still running. On the screen, the broadcast showed Shinguu Sanagi filming them.

“What is this lol?”

“Did they suddenly go outside?”

“Weren’t they resting in the boss room?”

“Everyone looks confused.”

“Wait, Tia-chan is—”

“—So you’re the one who “sealed” it!”

Shouting at the top of her lungs, Tia took off running. In the blink of an eye she had covered fifty meters, and it looked like she struck someone who had been there.

Tooru still couldn’t understand what was happening and could only stand there like an idiot—but even so, a corner of his mind began to turn.

Why had Tia suddenly run off and punched someone?

Because that person was a bad guy, obviously.

There was no need to think about that. She had thought he needed to be hit, so she went and hit him. Then what about the word sealed that Tia had used…? Did she mean that the Dungeon had been sealed?

Had the Kamioka Dungeon been sealed, forcing everyone inside to be expelled… outside?

But sealing a Dungeon?

For what reason? By whom? And how, in the first place?

“Tooru! I think this guy was there at that meeting!”

Dragging the person she had knocked out by the collar, Tia ran back. Like a careless delivery driver, she flung him toward Tooru.

He was an elderly man in a suit.

He had apparently been knocked out quickly and with precision—despite being punched, there were no visible external injuries. His eyes were rolled back, and he seemed to be breathing, but the sight of an unconscious elderly man was oddly unsettling. Tooru found himself thinking something so out of place.

“Uh… so, who was this guy again? I know he was there, but…”

Scratching his head as he searched his memory, Tooru found that the face and name simply refused to line up.

After waiting a moment to make sure the camera was focused on the man lying on the ground, he glanced down at his device. Judging that the comments would be more reliable than his own memory, he checked the stream.

“Isn’t that Sasamori Takeshi?!”

“Why’s that scandal-hit Assemblyman Sasamori here?”

“How do you forget him, Tooru-bro?”

“Apparently he’s Assemblyman Sasamori,” Tooru said.

“Don’t cheat by reading the comments lol.”

“I left halfway through that meeting. Why’s this guy getting flamed, anyway? No—well, I get why he’s getting flamed, but… why is he here at this hour, in a place like this? And what about the Kamioka Dungeon…?”

“As I said, I think this man’s the one who sealed it. Circumstantially, he’s the only possibility. Or else it’s someone who brought him all the way out here—but either way—”

“Tooru-kun!”

Cutting into the discussion between Tooru and Tia, Anthem’s leader, Saitou Megumi, raised her voice. Not just loudly—her tone and expression were closer to desperation, enough to make even Tooru flinch.

In her hand was a mobile device.

She must have just finished a call with someone.

“Listen—calm down… and hear me out, okay? The Noumi Dungeon and the Sugai Dungeon have both… gone into a Dungeon Stampede…”

◇◇◇

Snap.

Like a crude jolt of electricity from directly connecting two live copper wires, a violent awakening surged through him. The moment Tooru’s awareness shifted from something distant to something personal, his mind sharpened so intensely that it surprised even him.

Perhaps it was thanks to his experience with the Kagetsu.

Or perhaps because he was connected to Lightbringer.

There was no way to confirm either, so he didn’t waste a single thought on it. Instead, in one swift motion, Tooru checked the sky, found the position of the moon, swept his gaze around the area—and then broke into a run.

“Tooru!? Where are you going?!”

Tia followed after him, startled but keeping pace. She was probably accustomed to emergencies. Back when she wielded the holy sword in life, she must have survived more battlefields than anyone could count.

“Sugai Dungeon.”

He spat the answer out tersely, not even slowing, and kept running.

They reached their destination almost immediately. The parking lot. Assuming that the spot where they had been standing earlier marked the former entrance to the Kamioka Dungeon, he triangulated the location of the lot. It had mostly been guesswork, but it turned out to be correct.

He pulled the key from his pocket, unlocked the car, tossed the rebar club into the back seat, and slid into the driver’s seat. Tia opened the passenger door, swung Lightbringer from her back around to her front, and slid into the seat while hugging the sword close.

He started the engine and shifted into reverse—

Bang!

Something slapped against the window. A small palm.

It was the elf, Irselia. Catching up to Tooru at a full sprint would have been trivial for her.

“You said you were heading to the Sugai Dungeon!”

Apparently unwilling to waste time making him roll the window down, Irselia shouted loudly enough for Tooru to hear from inside the car. Tooru, for his part, found shouting bothersome and simply nodded.

“We’re heading to suppress the Dungeon Stampede at the Noumi Dungeon. Whoever finishes first heads to support the other. Agreed?”

“Sure! Let’s do that!”

Tia answered on her own initiative, but Tooru put off complaining about it. Irselia stepped away from the car, so he finally pressed the accelerator, turned the wheel, shifted the lever back into drive, and pulled out.

Even if he was in a hurry, he wasn’t a professional driver. Flooring the accelerator and expecting to keep control wasn’t an option. He pushed it as hard as he could—within the limits of what he could manage.

They exited the Kamioka Dungeon parking lot and moved from a city road onto a prefectural road. Whether heading to the Noumi Dungeon or the Sugai Dungeon, it would take about fifteen minutes from here.

Ignoring the speed limit, if the road was clear… even then it would take ten minutes.

In six hundred seconds, how much damage could occur?

That would naturally depend on the type and scale of the Dungeon Stampede.

At present, they knew nothing at all—so worrying about it was pointless.

“These twisty roads make it frustrating,” Tia said, narrowing her eyes at the prefectural road illuminated by the headlights.

“Yeah,” Tooru replied, and nothing more.

Mountain-heavy prefectural roads in Japan were always winding. He had never once found that frustrating—until now.

“You’re planning to do something about the Dungeon Stampede at the Sugai Dungeon, right?” Tia asked.

“Yeah.”

“Why?”

“…Huh?”

“I mean, you don’t actually have any obligation, do you? No one’s telling you that since you wield a holy sword you have to purge evil, like they used to tell me. No one’s saying that having great power means you must shoulder great responsibility—at least, not yet.”

There was a faintly world-weary tone to Tia’s voice.

She had probably had that sort of responsibility forced onto her in exactly the way she described. Tooru could infer that much—and at the same time, he couldn’t help thinking that it was Tia herself who hadn’t thrown that responsibility away.

If she had truly hated it—if she had genuinely thought to hell with it—

then she could have abandoned everything and disappeared somewhere far away.

“What do you mean by sealed?”

So Tooru asked—something slightly off the mark, perhaps because of it.

Tia made a face like she had just put something sour in her mouth, then nodded.

“There’s an item that can erase a Dungeon. …Or rather, there was one in the world I came from. Normally, a Dungeon disappears if you destroy its core at the deepest level, but there were items that could disable that core from the outside.”

“Then why did sealing the Kamioka Dungeon cause the Noumi and Sugai Dungeons to go into a Dungeon Stampede? There’s probably a connection, right?”

“I’m guessing here, but the three Dungeons are probably linked. The reason you stepped on a teleport trap in the Sugai Dungeon and ended up in the Kamioka Dungeon is likely because they’re connected in terms of mana. Say the system as a whole shares sixty units of mana across three Dungeons, and the Kamioka Dungeon had a capacity of thirty—”

“So when the Kamioka Dungeon vanished, those thirty units flowed into the remaining two. They exceeded their capacity, and that triggered a Dungeon Stampede.”

“Probably, yeah.”

It was consistent with the idea that leaving a Dungeon unattended would eventually cause a Dungeon Stampede. In the end, exceeding a Dungeon’s mana capacity was what made things dangerous.

In that sense, Tooru’s work as a bottom-tier cleaner, endlessly hunting low-floor monsters, hadn’t been meaningless—but well, given how things had turned out anyway, maybe it had all been pointless after all.

“Hey, Tooru. You still haven’t answered my question from earlier.”

“What question?”

“Why you’re trying to do something about the Dungeon Stampede at the Sugai Dungeon.”

“It’s close to my place.”

“…Huh?”

Tia probably made a blank, idiotic face—or so it seemed to Tooru. He was driving at a pretty high speed, so he didn’t really have the luxury of staring at the passenger seat.

Because of that—or perhaps regardless of it—Tooru ignored her expression and the confusion she was clearly feeling. He pressed the accelerator a little harder and let his thoughts spill out.

“It’s about fifteen minutes by car from my apartment to the Sugai Dungeon. There’s a twenty-four-hour supermarket on the way—I used to stop there a lot after work. Go a little farther and there’s a convenience store, too. In the run-down apartment next to mine lives a cat-beastkin mother and child. I don’t know why, but the mom’s weirdly familiar with me. She works in nightlife, and sometimes at night she leaves Mika with me. Mika’s pretty quiet for a kid her age—thoughtful, I guess you’d say. I think her birth and circumstances made her that way. I can’t really improve her situation or anything, but… she’s not a bad neighbor. It’s not like I do anything special—just watch over a lonely kid for a bit, and when her mom gets back, she goes home on her own. It just makes me feel like I did something good. Just a little.”

“…Tooru…”

Tooru didn’t care what kind of expression Tia had on her face. What irritated him was the simple fact that a car moving along a prefectural road at ninety kilometers per hour felt unbearably slow.

“When I was seventeen, I went with my parents to visit my grandparents, and we got caught up in a Dungeon Stampede. It was a pretty small one, but everyone in my family except me died. I don’t hold a grudge against the explorers who suppressed it. I don’t think they could’ve done better. Everyone did what they were supposed to do, within their limits. Basically, we all live our lives thinking we’re doing the right thing. Saying ‘we should’ve done more’ is just nonsense. It’s just that we couldn’t do more. That’s all there is to it. For me, you, everyone else.”

There were countless choices spread out before him.

If it had been Hayasaka Tooru up until not that long ago, he could have quit being a cleaner at any time and gone to a vocational school to get a proper job.

But he hadn’t.

Even if it was a D-rank Dungeon with no real appeal to explorers, if no one went in and killed the monsters, the likelihood of a Dungeon Stampede would keep increasing.

As long as Hayasaka Tooru kept working as Tooru the cleaner, he could reduce that risk, however slightly. Someone else might have done it if he hadn’t—but in reality, for three years, the city’s Dungeon Division had continued to contract Hayasaka Tooru to clean the Sugai Dungeon.

He hadn’t become an explorer, but he had still stayed involved with Dungeons and kept fulfilling his tiny role. No matter what anyone thought of him, that had been enough.

It was self-satisfaction.

And what was wrong with satisfying himself?

Even this time—getting angry at the elf, then joining Anthem after a cheap apology—it wasn’t because he’d forgiven them from the bottom of his heart. His heart wasn’t that big. In the end, it was because accepting the deal let him keep indulging that self-satisfaction.

He even thought to himself that he shouldn’t have gotten angry in the first place—but both feelings were genuine.

He didn’t want to sell even his soul for volunteer work, but he wasn’t so inflexible that he couldn’t put up with a little irritation. He’d been pissed, so he’d shown it. He’d gotten an apology, and he’d been paid. And as a result, he’d gotten to accompany a Dungeon expedition.

“If my parents had known a Dungeon Stampede was going to happen, they never would’ve gone to my grandparents’ place. They could’ve evacuated my grandparents ahead of time, too. But that didn’t happen. Of course it didn’t. Ordinary people can’t see the future. There was nothing anyone could’ve done about it. No one.”

The kei car’s engine began to scream at high RPMs.

Before he realized it, he was pushing close to one hundred and twenty kilometers per hour.

“—You have me now.”

A hero’s voice, clear and resolute, resonated deep in his chest.

Even so, Tooru didn’t look toward the passenger seat.

Ahead—now finally close enough to make out clearly—the entrance to the Sugai Dungeon came into view. At that place, Tooru’s workplace for the past three years, he could see something enormous moving.

Despite the surrounding night being almost completely devoid of streetlights, it was visible because the mana leaking from the monster’s body interfered with something in the atmosphere, producing a glow.

Just like the walls of a Dungeon.

A luminescent phenomenon that was, at its core—proof that it was fundamentally incompatible with this world.

“A gigantic serpent-type monster. A fantasy species based on local folk beliefs. Most of them lack reason and do nothing but rampage, destroying their surroundings with their massive bodies and devouring whatever’s nearby with those huge mouths. A monster that’s basically calamity given form.”

As she spoke, Tia—despite the car still being in motion—flung the passenger-side door wide open and, unbelievably, tore it off with a loud crash.

What had been a car door just moments earlier was discarded onto the road, and because they were moving at high speed, it vanished into the distance almost instantly.

Ahead loomed Orochi, larger than a two-story house.

It writhed violently, like an earthworm suddenly dug out of the ground. Just as Tia had said, that alone was enough to pulverize nearby trees and asphalt alike. The familiar Dungeon branch office was already in what looked like a completely devastated state.

“Hey—!”

Before Tooru could even finish thinking what the hell are you doing, Tia twisted her body mid-motion, still clutching the holy sword, and planted herself atop the kei car’s roof.

On the roof of a car traveling at one hundred and twenty kilometers per hour.

“If I get too far away from you, my manifestation will unravel. So get close—close enough that we might crash into that thing! I’ll definitely take it down, and I’ll protect you too!”

About a third of him thought, That’s insane.

The remaining two-thirds—

If she says it, then it’s probably possible.

“Guess I should be grateful to Anthem. Good thing I took the money.”

Saying that, Tooru pressed the accelerator down harder, steering straight toward the massive Orochi now clearly visible before him.