The Yandere villainess loves the useless engineer

The three of us eventually returned toward the village as the sun slowly began setting behind the forests.

Finn still looked traumatized.

"I genuinely think that was the closest I’ve come to dying."

I glanced toward him.

"You fought in a war."

"That was somehow less stressful."

Garrick walked silently beside us while carrying the oversized crossbow across his back. The hunter’s expression remained grim ever since we escaped the mine.

The sounds inside those tunnels clearly still lingered in his mind.

Eventually I finally spoke.

"I have a plan to clear the mine."

That immediately caused Garrick to look toward me suspiciously.

"...You say that with far too much confidence."

I continued calmly.

"The rats only control the mine because people keep trying to fight them directly underground."

"And your solution?"

My eyes narrowed slightly.

"We stop fighting them fairly."

Finn slowly groaned beside me.

"...There it is."

Garrick remained silent for several moments.

Then finally:

"What exactly are you planning?"

"Smoke. Controlled tunnel collapses. Kill zones near the entrances."

I looked ahead toward the distant hills.

"If we force the colony upward into narrow tunnels, rifles can thin them out safely."

Garrick still looked unconvinced.

"There are thousands of those things."

"Then we kill thousands."

The hunter studied me carefully after hearing that.

Not emotionally.

Not bravado.

I said it like I was discussing construction work.

Eventually Garrick sighed heavily.

"...You really are dangerous."

Finn pointed toward me immediately.

"I’ve been trying to tell people that."

I ignored him.

"We’ll need manpower though."

That caused Garrick to frown slightly.

"You want villagers helping with this?"

"We need people to move supplies, maintain fire lines, seal tunnels, and hold positions."

I looked toward him directly.

"Can you gather anyone willing to fight?"

Garrick immediately looked doubtful.

"I’ll help."

Then he shook his head slightly.

"But honestly? I seriously doubt anyone else agrees to this."

"That many people scared?"

The hunter gave Finn a flat look.

"You saw the mine."

Finn immediately nodded.

"...Fair point."

I remained thoughtful for several moments before finally speaking again.

"Find whoever you can."

Garrick slowly crossed his arms.

"And if nobody agrees?"

My expression remained calm.

"Then we do it with fewer people."

That answer somehow worried both Finn and Garrick simultaneously.

The next morning Finn and I departed from Blackwater Hollow and began the journey back toward Aldric territory.

Most of the trip passed quietly.

Mostly because Finn kept randomly remembering the rats and visibly shuddering every twenty minutes.

At one point he suddenly looked toward me.

"You realize normal people would abandon the mine after that right?"

"There’s too much nitrate there."

"You sound emotionally attached to explosives."

I didn’t answer.

Which honestly answered the question.

By the time we finally returned to Aldric territory, I immediately threw both myself and Finn into overdrive.

The next month became absolute chaos.

The shack transformed into a nonstop production center as workers constantly moved materials between the industrial district and my workshop.

Steel shipments arrived almost daily now from the separate factory complex deeper inside the territory. The expanded bloomeries and blast furnaces operated continuously while waterwheels powered presses, grinders, and casting systems day and night.

For the first time—

I actually had industrial capacity.

And I used all of it.

The rifle production line expanded first.

Using improved steel molds and more refined machining techniques, Finn and I managed to produce four additional rifles over the course of the month. Compared to the originals, these newer models were noticeably better balanced and more reliable.

The bullets became easier to mass produce as well.

My improved casting molds allowed workers to create ammunition significantly faster than before, which was critical because the upcoming extermination plan would consume absurd amounts of ammunition.

And unfortunately—

We were running out of nitrate.

Fast.

Every remaining reserve from the nitrate beds got used during preparation.

Gunpowder barrels filled sections of the shack while workers constantly packed cartridges and explosive shells beneath my supervision.

Finn looked increasingly horrified every day.

At one point he stared toward the growing explosive stockpile near the wall.

"If a spark hits this building, historians are going to find us orbiting the moon."

I barely even looked up from the workbench.

"Then don’t create sparks."

"That is NOT reassuring."

Meanwhile the steam engines continued improving as well.

Finn and I eventually completed two new engines during the month, both more refined than the original prototype. Improved pressure handling and stronger steel components made them noticeably more stable, though steam leakage still remained a constant annoyance.

Still—

The important part was power.

Because my upcoming plan required more than rifles.

It required infrastructure.

Smoke systems.

Airflow control.

Mechanical pumping.

Tunnel collapse operations.

Everything slowly came together piece by piece.

But during the final week of preparation—

I isolated myself almost completely.

Even Finn barely saw me.

Most nights strange metallic noises echoed from deeper inside the shack long after midnight while workers quietly whispered about whatever their young lord was building now.

Occasionally sparks burst through gaps in the workshop walls.

Other times loud pressure releases shook parts of the building hard enough to rattle nearby windows.

Finn eventually tried questioning me directly.

"What are you making?"

I didn’t even look up from my workbench.

"A weapon."

"That sentence concerns me greatly."

I continued adjusting several metal pipes connected to a reinforced pressure chamber.

"I need something capable of clearing tunnels quickly."

Finn slowly stared at the partially assembled machine.

"...Why does it have a fuel tank?"

I finally looked up slightly.

"Because fire spreads."

Silence.

Then Finn slowly backed away.

"...I don’t want to know anymore."

I returned to working immediately.

The rats underground had numbers.

Darkness.

Tunnels.

But I had spent the last month thinking about confined spaces and mass extermination.

And deep inside the workshop—

Something terrifying was slowly taking shape.

After nearly a month of nonstop work, I finally declared the preparations complete.

The shack looked like a war factory by that point.

Crates of ammunition filled entire corners of the building while rifle parts, steel pipes, mining tools, explosives, and mechanical components covered almost every remaining surface. Workers constantly moved materials between wagons outside while steam hissed from one of the newer engines operating nearby.

Even Finn looked exhausted now.

Dark circles sat beneath his eyes while soot permanently stained half his clothes.

"I think we industrialized sleep deprivation."

I barely looked up while tightening part of a pressure valve.

"We’re behind schedule."

Finn stared at me blankly.

"...That sentence should legally qualify as a threat."

Outside the shack several wagons had already been loaded for departure.

The supplies themselves looked bizarre when assembled together.

Steel pipes.

Small railway tracks.

Minecarts.

Two steam engines.

Explosives.

Ammunition.

Fuel barrels.

And enough tools to either reclaim a mine—

Or accidentally invade a small kingdom.

I eventually stepped outside while adjusting the rifle strapped across my back.

Five additional workers waited nearby looking somewhere between nervous and deeply confused. Most of them had originally been construction workers or metalworkers from the industrial district rather than soldiers.

Which honestly made sense.

I didn’t need warriors.

I needed people capable of building things quickly.

Finn glanced toward the loaded wagons.

"...You know normal people solve rat problems with traps."

"These aren’t normal rats."

"That stopped comforting me weeks ago."

The journey back toward Blackwater Hollow took several days due to the sheer amount of equipment we transported. The steam engines alone slowed travel considerably while the steel rails and piping added even more weight to the wagons.

By the time we finally reached Garrick’s cabin again, even the hunter looked visibly confused seeing the caravan approaching through the trees.

The moment Garrick stepped outside, his eyes immediately landed on the steam engines.

Then the steel rails.

Then the crates of explosives.

Then finally me.

Silence followed.

"...What exactly did you bring?"

I climbed down from the lead wagon calmly.

"A solution."

Finn muttered quietly behind me.

"That answer never leads anywhere good."

The workers began unloading supplies while Garrick continued staring at the absurd amount of equipment now scattered around his cabin clearing.

Eventually he pointed toward the rails.

"...Why are there train tracks?"

"Minecart system."

Then toward the engines.

"And those?"

"Steam-powered cable systems."

Then toward the explosive crates.

"...Should I even ask?"

"Probably not."

Garrick slowly rubbed one hand across his face.

"...You leave for one month and somehow invent mining warfare."

I gathered everyone together shortly afterward near the clearing outside the cabin.

The workers themselves still looked uncertain about the entire operation, especially after Garrick explained exactly how large the rats were.

One younger worker eventually raised a hand nervously.

"...So we’re fighting dog-sized cave rats?"

"Yes," I answered calmly.

The man looked deeply disturbed.

I ignored it and began explaining the plan.

"First we clear the upper sections near the mine entrance using controlled explosions."

I crouched slightly before sketching rough tunnel layouts into the dirt using a stick.

"We collapse unnecessary side tunnels and limit the number of pathways the rats can move through."

Garrick slowly nodded while studying the diagram.

"Force them deeper."

"Exactly."

I continued drawing.

"After that we install a rail system into the cleared sections of the mine."

One of the workers frowned slightly.

"A rail system?"

I pointed toward the wagons nearby.

"The minecarts."

Now even Garrick looked confused again.

I continued calmly.

"The carts will be attached to a steel cable connected to a steam engine outside the mine."

Understanding slowly spread across Finn’s face.

"...Wait." 𝙛𝒓𝒆𝙚𝒘𝒆𝓫𝙣𝓸𝙫𝓮𝒍.𝒄𝒐𝓶

I nodded slightly.

"The engine pulls the carts rapidly back out if anything goes wrong."

Now several workers looked impressed instead of confused.

I then drew another line beside the rails.

"Alongside the tracks we install steel piping."

Garrick folded his arms.

"For the smoke?"

"Yes."

The second steam engine would continuously pump smoke through the pipes deeper into the mine system. I planned to burn sulfur, oil, damp straw, pitch, and other foul materials to create thick choking smoke capable of spreading through entire tunnel systems.

"The smoke forces the rats to either flee upward or retreat deeper underground."

I looked around toward the others.

"Any rats emerging from the mine get shot outside where we have open space and prepared defenses."

Finn smirked slightly.

"See? Now it sounds less suicidal."

Then I continued.

"Once the smoke clears a section, workers extend the rails and pipes deeper into the mine before the rats return to that area."

One worker slowly realized the problem.

"...What about when they come back?"

"That’s why the carts exist."

I pointed toward the tracks again.

"If workers encounter rats while extending the systems, they immediately board the minecarts and the steam engine outside pulls them back to the entrance."

Silence followed for several moments.

Then one worker blinked slowly.

"...That’s actually genius."

Finn looked deeply offended.

"Please don’t encourage him."

But the more I explained the operation, the more even Garrick began understanding the logic behind it.

Nobody would fight the rats deep underground directly.

The mine itself would slowly become controlled territory section by section.

Smoke pushed the rats.

Rifles killed the exposed swarms.

Explosions sealed off dangerous areas.

Rails and steam engines allowed rapid movement and escape.

It wasn’t monster hunting.

It was industrial extermination.

Garrick stared toward me quietly afterward.

"...You really spent a month planning all this."

I looked toward the distant hills where the mine waited.

"The rats have numbers."

Then my eyes shifted briefly toward the steam engines.

"So I brought industry instead."