Chapter 14
“Magic energy… in fireworks?”
“There’s no mistake. Electronic devices have stopped working. The ambient magic energy density around here is rising rapidly… This is strange. Doing something like this—was it to unlock the magic network? Did someone apply for it…? No, that doesn’t make sense. Even if you raised the density this locally and this suddenly, there’s no way such a request would be approved…”
A sudden abnormal situation. And yet, the fireworks continued to be launched into the sky.
For now, it was just smartphones. But if the magic energy density kept rising this sharply, then throughout this entire area, electronic devices and industrial products with complex mechanisms would begin to malfunction or shut down entirely—just like inside a dungeon.
“…This is pretty bad, isn’t it, big sis?”
“Cars, elevators—things that carry people—might malfunction or stop. People could die. Akira, we need to hurry to the launch site… I’ve got a really, really bad feeling about this.”
That’s right. The concentration of magic energy in the air directly causes the same kinds of ‘electronic interference’ and abnormal atomic reactions that occur inside dungeons.
There was once a time when people tried to use heavy firearms inside dungeons. The result was disastrous: explosives detonated unexpectedly, metals reacted in unforeseen ways, heating up, deforming, and expanding. They couldn’t be used properly at all.
Even today, as magic energy has gradually spread throughout the world, new technologies—magic-based chemistry—have emerged and spread as well. But at the same time, malfunctions of existing industrial products and electronic devices have also become more common.
Of course, research is being done to prevent this, and technologies that allow devices to operate safely are being established.
But that’s only within cutting-edge research labs.
There’s no way ordinary products in a normal city are protected by such technology.
And besides… for magic energy to spread this rapidly, all at once…!
“Onee-san, this way! The reclaimed land should be just a bit past Odaiba—somewhere people aren’t allowed to enter!”
“Let’s go. This is… deliberate. Someone did this intentionally. Honestly, right now I curse my own sharp mind. This is probably… going to turn into a major disaster.”
“What… what do you think is going to happen?”
I called out to her as we ran, and she answered with an unusually tense expression.
Amid the growing murmur of the crowd—voices of confusion and panic swelling louder—she said it clearly.
“…Dungeon induction. The dungeon reacts to the sudden rise in magic energy, extends itself like probing tentacles, and expands. It’s trying to absorb the magic. Normally this never happens—because under normal circumstances, you’d never have such a massive amount of magical energy suddenly scattered outside.”
“W–What!? Dungeons have that kind of property!?”
“Humanity had already proposed the theory. And it turns out it was correct. But there was never a reason or a way to prove it, so it stayed just a theory on paper. But… this confirms it. Someone is experimenting.”
If what she said was true, a new dungeon would be born, causing massive effects on the surrounding ground.
Dungeons aren’t physically spreading underground in a literal sense—they expand as a kind of other-dimensional space. Even so, near the entrance, existing matter is violently displaced, and the effects spread outward.
And more importantly—newly formed dungeons have ‘blurred boundaries.’
I’d learned this in history class. After the war, a branch dungeon suddenly appeared in Ginza.
According to historical records, “grotesque beings overflowed from a massive hole that appeared without warning.”
In other words, freshly born dungeons don’t yet have their rules functioning properly.
Monsters can casually come out into the outside world.
“I’ve never heard of a new dungeon forming…”
“Neither have I, not firsthand. But this… has a high chance of becoming exactly that.”
Saying so, my sister vaulted over a restricted-area fence and rushed into the launch site—a vacant lot created by newly reclaiming land from the sea.
I followed after her. Around the devices that had been launching large numbers of fireworks via electronic control, bewildered staff members had gathered.
“Who are you!? This area is off-limits to unauthorized personnel!”
“This isn’t the time for that! Right now, the electronic controls on those launch devices and all external communication via smartphones are down, aren’t they!?”
“Y–Yes, that’s—”
“It’s happening across the entire venue! Everyone around here has lost smartphone functionality! I spoke with a specialist who’s knowledgeable about electronic issues, and according to them, this is all due to ‘magic-energy-induced electronic shutdown’! If this continues, a much larger accident could occur. First, remove everything from the launch devices that could cause secondary explosions—gunpowder and the like—get it all out!”
“What!? Is that really true!?”
“It is! And if it turns out I’m wrong, you can turn me over to the police later or whatever you want! Apparently… a massive amount of magical energy was embedded into the fireworks, and it dispersed into the surrounding area the moment the fireworks began!”
“W–What… no, but… could it be—”
“Do you have… some idea what might have happened?”
One of the staff members—probably the person in charge—spoke up.
“There is something suspicious about this fireworks festival. The fireworks used this time… briefly went missing. They were delivered by the supplier, but then they vanished without a trace. And before we knew it, they’d already been transported to the venue. We assumed it was just a delivery mistake on the supplier’s end…”
“I’ve heard enough. First, immediately unload the fireworks from the launch devices and store them securely. After that, everyone evacuate. There is an extremely high chance of further trouble occurring here. From this point on, this is the domain of us explorers. All civilians should leave the area at once.”
Putting on her cool, professional persona, my sister began issuing instructions to the staff.
They were momentarily taken aback by her appearance, but whether it was her commanding beauty or sheer presence, they yielded and immediately began following her orders.
“Even without launching them, there’s still a mass of magic energy here. The dungeon may have already taken notice. For now, I’ll have them pack all the fireworks back into the containers they were delivered in. Those should be treated to prevent magic energy from dispersing. It should buy us a little time.”
“Onee-san, what do we do next?”
“…I can already feel the dungeon’s presence. Or rather, this reclaimed land itself feels strange. From the moment I stepped in here, I’ve had this unsettling sense of ‘being inside a dungeon.’ This… might be a much larger conspiracy than we imagined. I didn’t want to drag you into something like this, Akira.”
“No, once I know about it, I can’t just ignore it. If a dungeon really forms, what do we do?”
“We watch to see whether a monster outbreak happens. If it does, we wipe them out. I don’t think there’s anything else to do.”
As she said this, she put on her weapon—her gloves—and fixed a hard stare on the containers where the staff had packed away the fireworks.
“Everyone on the staff. Leave this area immediately, and if possible, tell all the explorers in the venue to gather here. We don’t have solid confirmation yet, but… there’s a chance something major is about to happen here.”
“O-Okay! The ground’s been shaking for a while now… I don’t know what’s going to happen, but you take care too! You want us to call the explorers, right!? Then we’ll leave the rest to you!”
As the staff fled, the ground began to heave.
Staggering staff members ran away screaming in shock—and then it appeared.
Right in the center of the reclaimed land, a massive hole suddenly opened up, plunging deep into the earth.
And then… countless writhing shapes inside were illuminated by the lights of the launch site.
“…Akira, up to today you’ve fought barehanded so many times, I think you’ve built plenty of experience—landing your hits, activating techniques, controlling the flow of power.”
Staring at the huge pit—the entrance of a newly born dungeon—my sister spoke.
As usual, she sounded completely natural, acting as if she felt no tension at all.
“It’s time to move on to the next step. You’ll transfer the sense you’ve built up—your attacks and techniques—into a weapon. From today, sword combat is officially unlocked. And don’t you dare go easy on monsters—your big sister won’t forgive that.”
“…Roger. I finally get to see my beloved sword in action again.”
“It’s a pretty good sword, after all. …Let’s go, Akira. We’ve got kobolds mixed in with goblins. But this is a dungeon with blurred boundaries. They might not all be low-floor monsters—and there are a lot of them. If they get out of the reclaimed land, it’s game over.”
“Yeah. If we let them reach civilians, we lose. It’s a defense game.”
“We’ll hold the line until the explorers gather. Don’t worry—it’ll be fine. Your big sister is special, after all!”
“And as her disciple, I’m special too.”
“Big talk for a kid.”
“I’ll be an adult in two months.”
Trading light banter, we charged toward the horde of monsters.