The Yandere villainess loves the useless engineer

The blast furnace finally roared to life at full capacity.

Molten metal poured through carved channels in brilliant orange streams while heat flooded the workshop hard enough to make the winter air outside feel nonexistent.

Even after everything we had built so far, watching liquid iron flow from the furnace still felt unreal.

Finn looked even more stunned than me.

"...We made a fake volcano."

"More or less."

Using carefully prepared sand molds, we started forming rough metal components unlike anything Finn had ever seen before.

Some molds failed completely.

Others cracked apart from the heat.

A few pieces cooled warped and unusable.

But gradually—

The process improved.

Again and again I adjusted tiny details while Finn prepared fresh molds beside the furnace.

By the end, rows of rough iron and steel pieces covered the workshop tables.

None of them looked impressive yet.

Most were uneven.

Ugly.

Barely recognizable.

But that didn’t matter.

They only needed to be close.

Afterward came the exhausting part.

Filing.

Grinding.

Scraping.

Measuring.

The workshop became filled with the endless sound of metal being shaped by hand.

Thankfully, this world already had standardized measurements, meaning rulers, measuring rods, and precision tools already existed instead of needing to be invented from scratch.

Even then—

Precision was painfully difficult.

Tiny differences ruined alignment.

Some pieces had to be entirely redone.

Others required hours of careful adjustment before finally fitting correctly.

At one point Finn collapsed backward into his chair dramatically.

"...I quit. I want retire already."

I ignored him while continuing measure one of the components against a steel ruler.

At this stage, I had realized something important.

The hardest part of industrialization wasn’t mining minerals or producing materials.

It was precision.

Creating parts that matched exactly.

Still—

Slowly—

The strange mechanism finally began taking shape.

Wood was carved carefully and fitted around the metal frame.

Internal components were adjusted over and over until movement became smooth.

Then finally—

After hours upon hours of work—

Two completed creations rested silently upon the workshop table.

Long dark steel.

Polished wood.

Completely alien compared to every weapon this world currently used.

I stared at them silently.

Even I felt slightly stunned seeing them completed.

Because sitting before me was technology centuries ahead of this world.

Meanwhile Finn simply stared blankly.

After several long seconds, he finally spoke.

"...What in the hells are those supposed to do?"

I slowly smiled before carefully picking one up.

"Oh trust me."

I pulled the lever with a metallic click.

"You’re about to find out."

The two strange weapons rested silently upon the table while Finn stared at them nervously.

"...So?"

"So what?"

"How do they work?"

I pointed toward the long steel barrel.

"A metal projectile gets launched out of here at extremely high speed."

Finn blinked.

"...Using magic?"

"No."

"...Then what launches it?"

I pointed toward the sealed black powder containers nearby.

"Controlled explosions."

Finn immediately took several steps backward.

"You are completely insane."

I ignored him while inspecting the rifle’s mechanism.

The weapons themselves had already taken weeks of work.

Sand molds created rough shapes before we painstakingly refined every component by hand using files, grinding stones, and measuring tools.

Even tiny imperfections caused massive problems.

But now came another issue.

A firearm without ammunition was useless.

For the next several days, the workshop became filled with strange sketches and tiny metal components while I tried explaining the concept to Finn.

"The projectile goes here," I explained while holding up a small metal casing.

Finn frowned.

"...Why put it inside metal?"

"Because the casing keeps everything contained."

I pointed toward the different sections.

"The powder sits behind the projectile inside the casing."

"And then?"

"The weapon strikes the primer located at the back."

Finn stared blankly.

"...And?"

"The primer is a sensitive ignition point."

His expression slowly changed.

"...Wait."

I nodded.

"The strike ignites the powder."

Finn immediately looked horrified.

"So the gun is just repeatedly setting off explosions directly beside your face?"

"...More or less."

"That is the worst thing you’ve ever made."

I ignored him and continued refining the tiny components.

Some casings cracked.

Others warped.

Several failed fitting inside the rifles correctly.

One experimental round jammed the mechanism badly enough that Finn threatened throwing the entire weapon into the river.

Still—

Progress continued.

Measurements became more consistent.

The mechanisms smoother.

And eventually a couple completed cartridges lined the workshop tables beside the rifles.

Finn carefully picked one up between two fingers.

It looked tiny.

Harmless.

Yet after watching my earlier powder tests—

He no longer trusted anything I created.

"...You know," Finn muttered slowly, "I think swords were perfectly fine."

I simply smiled while loading one of the cartridges into the rifle.

"No."

I pulled the lever with a metallic click.

"They were just outdated."

The forest behind the workshop had gone completely silent.

Finn stood several meters away beside a tree while staring nervously at the rifle in my hands.

"I still think this is a terrible idea."

I ignored him while adjusting the weapon carefully.

A single handcrafted cartridge rested inside the mechanism.

Just one.

After how long it took make them, neither of us wanted waste it.

Further ahead, an old steel helmet rested atop a wooden stump.

Finn glanced between the helmet and rifle uneasily.

"So let me understand this correctly."

I pulled the lever again with a metallic click.

"This thing creates an explosion beside your face..."

"Yes."

"...Then launches metal hard enough kill someone?"

"Yes."

"...And you want test it while I’m standing nearby?"

I looked toward him blankly.

"You can stand further back if you want."

Finn immediately moved several more steps away.

I slowly raised the rifle.

Even I felt tense.

This was the first true test.

If something failed:

- the barrel could rupture,

- the mechanism could break,

- or the cartridge could explode incorrectly.

The risks were very real.

I steadied my breathing before aiming toward the helmet.

Then—

I pulled the trigger.

BOOOOM.

The explosion shattered through the forest like thunder.

Smoke burst violently from the rifle while birds erupted from nearby trees in panic.

Finn physically flinched.

"WHAT IN THE HELLS—"

A loud metallic crack echoed a second later.

The helmet flew clean off the stump before tumbling violently through the dirt.

For several seconds—

Neither of us moved.

Smoke drifted slowly through the cold air.

Finn stared at the destroyed helmet.

Then toward the rifle.

Then back toward the helmet again.

Slowly—

The color drained from his face.

I carefully lowered the weapon before walking toward the target.

The front of the helmet had been completely punctured through.

Not dented.

Not cracked.

Pierced.

Cleanly.

Finn walked over silently before picking the helmet up with shaking hands.

"...Leon."

His voice sounded strangely quiet.

"If a knight was wearing this..."

I looked toward the hole silently.

"He’d be dead."

The forest became quiet again.

But this time—

The silence felt different.

Because both of us understood now.

This weapon was not some clever invention.

It was the beginning of something terrifying.