We walked through the city a demon had destroyed.

Our goal was to find that demon, and they were probably looking for us themself after we burned down their underling.

Whoever found the other first would have an overwhelming advantage.

Our advantage was that we had rendered the sensors of his underling useless.

We had discovered that it could detect enemies by their carbon dioxide levels.

It didn’t react to meat, but it ate a pig. Even when I burned it, it expressly thrusted its ivy and branches into the flames. That was why the fire spread so far.

The reason for that last reaction was also simple. It was because the increase in carbon dioxide concentration caused by the spread of fire made the monster think that its prey had arrived.

And so, as a countermeasure to that, I dissipated our exhalations into the air before sending them to the sky.

The demon was sharing their senses with their underling. That was why this countermeasure was like a double-edged sword. After all, no creature could escape from the eyes of the monster tree, so they could assume that we were right where the monster wasn’t growing its plants.

…And assassins were those who exploited such assumptions. “We’ve got cameras, so we’re safe”, “We’ve got guards, so we’re safe”, “We’ve got military dogs, so we’re safe”. Those who depended on this kind of “safety” made for easy prey.

[Lugh-sama, how will you find the demon?] (Lugh)

[I’ll use wind-based searching magic to scour the city. And if that’s not enough to find them, I’ll smoke them out in a slightly rough way.] (Lugh)

We were walking while slipping through the green monsters.

We remained alert to our surroundings and searched for the enemy.

And I dropped a few things here and there.

This city wasn’t particularly large, so it took about two hours to go around.

I couldn’t say if it was fortunate or not, but we hadn’t encountered the demon.

[Right back where we started, huh. Then let’s do it the hard way.] (Lugh)

[Say, those things you’ve been scattering all over the place since earlier, are those what I think they are?] (Dia)

[That’s right, those were special Fahr Stones.] (Lugh)

Indeed, I had been scattering Fahr Stones all around the city.

All of them were specially designed for deflagration and prepared for this very day.

A total of twenty-two stones.

That much was enough to burn down the entire city, and I arranged them for optimal efficiency.

[Um, Lugh-sama. Fahr Stones don’t explode unless you fill them up with mana to their critical point, correct? Then isn’t pointless to drop and leave them behind?] (Tarte)

[That’s for sure, but I’ve made the arrangements needed to detonate them. I’m casting a spell that Dia and I created together. A technique that absorbs the mana filling the atmosphere. The time they reach their critical point can be adjusted depending on the strength of the absorption. In other words, those are time bombs. Twenty-two time bombs, all calculated to explode simultaneously.] (Lugh)

[Then this means… Only one of them generated a deflagration with ridiculous firepower, but twenty-two of them… and all at once at that… Just how much damage would that cause…?] (Tarte)

[The whole city will be burned down. That’s how it works.] (Lugh)

This was a tactic I couldn’t resort to if there was a possibility of survivors being in the city.

However, there couldn’t be any survivor in a city covered with green monsters.

And I had confirmed with the government that I was allowed to do whatever it took to defeat the demon.

In that case, they wouldn’t mind if I burned down the entire city.

[Say, Lugh, what’s the point of doing this? Killing demons is a useless effort if it’s not with your【Demon-Slayer】spell, right? I know that monster tree is annoying and dangerous, but wouldn’t this be a waste of Fahr Stones?] (Dia)

[This is to harass them. You’ve seen how that monster tree eats people, converts them into mana, and stores it, right? It must’ve consumed a whole city because it wanted tons of mana for some reason. …So it could be that using mana to increase the number of monster trees and build up an army was the purpose itself. Looking at it that way, if we destroy what they’ve worked so hard to build, then the demon will lose their composure. We went all around the city and couldn’t find our enemy. So we’ll piss them off and make them come to us.] (Lugh)

While we were talking about this, we went outside the city.

If we stayed inside, we would be burned to death.

Besides, it’d be easier for us to find the enemy and harder for them to find us if we had a bird’s eye view from outside.

We made a deep trench a few dozen meters away from the entrance of the city and hid in it.

Using a special telescope, I could see the city from inside our hole.

[According to my calculations, it’ll begin in about a minute.] (Lugh)

There was a margin of error depending on the density of the mana in the atmosphere, but it would be about ten seconds at most.

The Fahr Stones had probably begun to crack by now.

Starting now, all that mana amassed by the demon would be destroyed, along with all her mass-produced underlings, until this entire city was in ruins.

Even the most mild-mannered of people would lose their temper over this.

…Anger clouded anyone’s judgement. And this was an extremely effective way to drive our enemy mad.

[Here it comes.] (Lugh)

I could feel the overwhelming increase in mana from where I was.

[Girls, don’t stick your heads out of here no matter what. This trench is guarded by a wind barrier to keep out the heat and the flames. If you come out of here even a little bit, you’ll die.] (Lugh)

Even if we weren’t directly hit by the flames, an explosion of this magnitude alone would kill us anyway.

And it would burn up all the oxygen in the area. If we breathed this oxygen-deficient air, we’d be out in one shot.

[Got it.] (Dia)

[Y-Yes, sir.] (Tarte)

Tarte clung to me out of anguish, and Dia saw her and followed suit.

Ten seconds later, it happened.

The world was engulfed in red. Crimson flames were passing over the trench.

Everything turned red.

A deflagration packed with the firepower of twenty-two stones, or in other words, six thousand six hundred people’s worth of mana, had repainted the world itself in red.

The roaring flames don’t spare anything.

They submerge every little thing, proliferated, and then, everything disappeared like it had never truly been there.

Flames needed air to burn.

I had filled those Fahr Stones with wind mana to supply them with air, but in the end, even all that was burned up in an instant.

The next moment, due to the loss of air, wind came rushing in from the surrounding area like some sort of cyclone, and even the few buildings that barely remained intact were shattered and blown away.

It was like a nightmare.

If we hadn’t stayed in our hole, we would’ve been blown far away too.

When everything was over, we took turns looking out through my telescope.

It appeared that the girls were still too afraid to come out of the hole.

[The city… It’s gone.] (Tarte)

[…This is unheard of. To think a single mage could not only destroy a city, but outright annihilate it.] (Dia)

Calling it a destruction was an understatement.

This was an annihilation.

The city disappeared without a trace, and what used to be a city was now a wasteland.

This was the result of using twenty-two Fahr Stones efficiently.

There was really nothing left.

[Hey Lugh, could you do the same in the royal capital if you felt like it?] (Dia)

[I could. All I’d have to do is sneak into the royal capital, place the Fahr Stones in the right places and escape. It’d be easy. That’s why the fact that I can do that must be kept secret. Otherwise, they’ll label me as dangerous.] (Lugh)

I could put the blame for this entire catastrophe on the demon. No matter how much they said I was allowed to act however I wanted, if they knew I wiped out this city, there’d be no telling what kind of complaints I’d get later.

Besides, my life was on the line.

[Yeah, you’re right. From the point of view of the higher-ups, you might be scarier than the demons. Good thing there weren’t any guard today.] (Dia)

[If they had been here, I would’ve used different means.] (Lugh)

A human who could wipe out a city in a few hours if he felt like it.

From the point of view of the rulers, such an individual would bring nothing but dread.

As long as the threat of the Demon King and the demon race remained, they would let me live, but once that threat was gone, they would eliminate me.

I could figure their train of thoughts.

“If by any chance, the boy went crazy, if he was bought off by another country, or if he had the ambition to take over the kingdom, this would be the end of our country.”

Of course, I had no intention to do that. But the mere fact that it was possible for me was already a danger.

Eliminating someone or something for safety reasons was a very rational idea.

…But Epona might go insane after defeating the Demon King because of the way she’d be treated based on this rational judgement.

If I was gonna be serious about saving the world without removing Epona, then I had to think of a way to only remove her hero powers.

I was just a human being, but I figured out a way to kill demons. So this wasn’t unfeasible.

[I wonder if the demon survived that.] (Dia)

[They may have died from that, but they’ll come back to life. Now, I wonder if that demon will be able to keep their cool after having everything they’ve built up blown away. If they keep hiding after taking such a beating, I’ll give up. Once I do, they’ll most likely repeat the same process in another city, which I’ll blow up again. Then I’ll wait for their patience to run out. Although I’d rather not do that.] (Lugh)

I took a look outside from inside the hole.

I was checking the city… or rather, the wasteland that was originally the city, to see if there were any movement.

This was a game of finding the enemy first, and patience was the key.

It must’ve happened two or three minutes later.

There was an explosion.

The source of that sound was in the center of what used to be the city.

I could feel the sound of the earth shaking from where I stood.

[Raaaaaaaaaaaaaaaaaaaaahhhhh…! Humaaaaaaaaaaaannnnnnnnn…! How dare yoooooooouuuuuuuuu…! The forest… The forest I worked so hard to grooooooooowwwwwww…! Just a little more… Just a little more and it would’ve borne fruuuuuuuiiiiiiiit…! I’ll kill yoooooooouuuuuuuu…! Kill yoooooooooouuuuuuuuu…!] (Demon)

He was enraged.

He was screaming, rampaging and wailing.

He was a humanoid demon with a black horn and a green shell, like a rhino beetle. His upper body was particularly massive, and the sharp edges of his shell made him look very aggressive.

Since he was manipulating trees, I thought the demon himself was of the same kind, but surprisingly enough, he was a combination of a human and an insect.

…A powerful enemy that combined defense, power and speed.

How bothersome.

But apparently, this match was in the pocket.

One way or another, we were the only ones who found the enemy.

In that case, the rest was easy. We just had to kill him.

[Dia, Tarte, on my signal, you attack from the front, and I’ll flank him.] (Lugh)

[So we’re going with that plan.] (Dia)

[I will protect you, Dia-sama!] (Tarte)

Dia set up the demon-slaying field while Tarte protected her.

And I would kill him from his blind spots.

We had to work together as a team to kill this demon.

…This was the first time our demon-slaying field had been put into action. And it was also our first time using this spell to kill this guy.

Even so, I wasn’t worried.

There was no one our team couldn’t assassinate.

I trusted Dia and Tarte enough to believe that.