Nest-Building Akito

I came here with Rirya, to her home.

After circling through a maze of underground tunnels, what we reached wasn’t a house so much as a secret base built by kids in the back hills.

They dug deeper, turned the hole into a home.

Fine. Living underground suits a monster girl, after all.

But what caught my eye was this:

“Nobody else around?”

Just one house. That’s it.

“Actually… in our clan, one girl leaves every year, strikes out on her own, leaves the old settlement behind, and starts a new one.”

“Huh.”

“She builds a new settlement, raises her children there.”

“Sounds like ants or bees.”

“But me… I’m hopeless at it.”

“Hopeless?”

Rirya nodded, stepped inside her home.

I followed. And then I understood.

Inside the house, there were tables and beds and various other furniture—but all of it was hideously made.

The table legs were uneven, and the bed was just a pile of grass.

Never mind that—backyard forts built by kids are way better.

“So that’s why you asked me if I could make things?”

“Yes…”

Lira lowered her head, embarrassed.

Well, that makes things simple.

“First, let’s build a house. Materials… I’ll skip hauling them up from the surface. Let’s just produce them with magic. Anything else—”

“Kyaa!”

Lira suddenly screamed.

“What’s wrong?!”

“Ah, that…”

Lira pointed. The wall of the underground passage had collapsed. A giant snake was emerging.

Bigger than an anaconda—easily a full head larger. Its body was thick as a meter-wide log.

Not just big—its fangs dripped with a sickly, venomous liquid.

It’s got poison, all right.

“W-why’s a Zmya here…?”

“Zmya. That’s what it’s called?”

“Yes.”

“Not one of your kind?”

“No! Don’t lump me with something like that!”

Rirya flinched violently. Big snake and snake-woman—thought they were allies, but nope.

“Anyway, let’s get out of here.”

Rirya was already backing away.

“Not even Ilya’s Spring?”

“If I made that, I’d never get near it myself.”

Ah. Right. Monster girl, after all.

…What’s the difference between a monster and me, really?

Lost in thought, I stepped closer to the Zmya. Dodged its gaping mouth, then slammed it square across the face.

Goth! Felt like hitting solid rock.

“Hard as stone.”

"Hard! Not just that—strong, too. One of those nasty ones that crush prey, dissolve them with poison, and eat slowly. Seriously, let’s get out of here, messenger—"

Drawing out the True Eternal Slave, she slammed it with magic-laden force.

Harder than expected, but the extra surge of magic cleaved through its head with a clean snap.

"Maybe this’ll be useful for something. Rirya, is this a unique individual… or part of the Zmya species?"

"……"

Rirya was speechless.

"Rirya?"

"……"

"Hey, what’s wrong?"

Waving a hand in front of her face.

"——huh."

"What’s the matter?"

"Y-you’re strong, messenger-sama…"

"…You didn’t think a divine messenger would be strong?"

"…I was scared of the Zmya…"

Thought even a divine messenger couldn’t beat it.

Well, whatever.

"Anyway, is this a unique one? Or just another of its kind?"

"Um, well, it's rare, but this is the kind of species..."

"Huh, that's reassuring."

If it were just an individual, it'd be a one-of-a-kind material—troublesome. Better to have it as a species, even if rare.

That’s what I thought when I muttered "reassuring."

"Wait... you're saying that's reassuring...? Maybe the messenger’s even more impressive than we thought?"

Rirya mumbled something.

I ignored that for now and mentally adjusted my plan.

If I can’t make Ilya’s Spring, I’ll have to build the defense and counterattack systems even more carefully.

Maybe I should treat this like a full-scale underground fortress.

☆

Cutting through the wall with the True Eternal Slave, infused with magic. It felt like melting butter with a hot knife—expanding the underground caverns with a smooth, dissolving motion.

Vertical, horizontal, height.

Expanded everything—until it became a massive underground hollow.

Made the half-basketball court—ring and all—fit snugly inside.

The volume was roughly five times that of the original hole.

Good enough here. Spacious now. Later, I’ll build something like a house, or a mansion, or a castle.

From what I heard, Rirya’s the new queen of the colony. That’s her role now.

Standing in front of the hole Zmium emerged from, she starts digging again with her slave sword.

Digging a narrow path—just wide enough for one person—to go a ways. Then, carving out a smaller space, about a quarter the size of the previous one.

Pulling out DORECA, she sets up a magic circle at the entrance.

“What’s this?”

“Rirya, bring over the table that was over there.”

“Oh—yes.”

Rirya, as instructed, carries over her lopsided table she made herself.

“I’ll be using this.”

“Using it… I don’t know what it is, but go ahead.”

Permission granted. She breaks the table apart with the sword and places the pieces inside the magic circle.

The materials came together—wooden door formed in an instant.

“W-w-what!?!”

Rirya, stunned.

“A door… in a second!?”

“Divine power. My power.”

“Amazing!”

“Let’s add an attack system on this side. Since it’s a cave, we’ll route the paths cleverly—draw enemies right here.”

Muttering as she thinks.

Getting a little excited now.

Not just town-building like before. More like… dungeon crafting.

Same general idea, but totally different.

Like Tetris and Puyo Puyo.

Like Mario Kart and Gran Turismo.

Street Fighter and Virtua Fighter.

That kind of thing—familiar, but not the same. A fresh feeling.

Pulling out DORECA, she slaps magic circles onto the wall—space, room, wall—then activates them with magic, emergency production.

“What… is that, my lady?”

“This?—Just in time, actually.”

Just as I was about to explain, the wall *bop*—a hole ripped open, and a monster burst into the room.

Big as a large dog, a mole-like thing.

“W-what now…”

“Come on, this way.”

I grab Rirya’s hand and pull her out of the room.

“W-won’t we fight?”

We’ll fight if it goes south, but first—let’s see what happens.

We peek back into the room together.

The monster chased us right through the center—just as it passed.

Dok-dok-dok-dok! Dozens of arrows shot out from the walls.

One second it was moving, the next it was a pincushion. Fell over. Stopped.

“Waaah!”

“Automatic defense system. Nina accidentally built it. Tried to install it on a battleship, but it didn’t fit. If we keep building stuff like this, Rirya won’t have to fight at all—just let the walls do the work.”

Thank you… thank you so much, messenger-sama!

I smiled back at Lila, her eyes sparkling, and then I thought further.

Assuming food, clothing, and shelter would continue as before, what else would be needed if we were turning it into a dungeon?