The Yandere villainess loves the useless engineer

Winter had fully arrived.

Snow blanketed the forest surrounding the workshop while freezing winds howled endlessly through the trees. Frost covered the roofs of the bloomeries each morning, and the river powering the waterwheels had begun forming thin sheets of ice near the edges.

The entire place looked dramatically evil now.

Especially at night.

Two roaring furnaces illuminated the snowy clearing with orange light while black smoke drifted into the dark sky overhead.

It looked less like a workshop and more like the hideout of two industrial cultists.

Which honestly—

Wasn’t entirely inaccurate.

I stood near the nitrate bed while stabbing a metal rod into the steaming pile.

Thankfully, the internal decomposition process still produced enough heat to prevent it from completely freezing.

Still—

We had started covering sections of it with straw and heated ash to keep the temperature stable during colder nights.

Finn stood several feet away holding his sleeve over his nose dramatically.

"I can’t believe we spent months building a pile of warm shit."

"It’s called chemistry."

"It’s called a crime against nature."

I ignored him and crouched beside the nitrate bed thoughtfully.

The decomposition process was progressing well.

Eventually, we’d be able to extract usable potassium nitrate from it.

And once that happened—

Gunpowder.

Real gunpowder.

But while that continued developing slowly in the background, steel production had continued dominating most of our time.

And honestly?

Business was thriving.

Over the past few months, Finn and I had refined multiple useful steel types by experimenting with carbon ratios and heating methods.

Hard steel for blades.

Flexible steel for springs.

Dense reinforced steel for tools and structural support.

Several blacksmiths in nearby towns had practically begun fighting over our shipments.

One merchant even tried bribing Finn for information about our production methods.

Finn had apparently convinced him the secret ingredient was "river rocks blessed by earth spirits."

Somehow—

The merchant believed him.

At this point I honestly couldn’t tell whether Finn was a genius or an idiot.

Probably both.

I stepped back toward the workshop while brushing snow off my coat.

Inside, warmth immediately hit me from the active furnace and forge.

Metal tools lined the walls while pages upon pages of sketches covered nearly every table.

And at the center of it all—

Sat the next step forward.

A rough sketch of a steam engine.

Finn walked over carrying two mugs of heated tea before looking down at the design suspiciously.

"...So explain this thing again."

I pointed toward the cylinder sketch.

"Water gets heated into steam."

"Okay..."

"The steam expands and creates pressure."

Finn nodded slowly.

"...Still following."

"That pressure pushes a piston."

His eyes immediately glazed over.

"...You lost me."

I sighed.

"Hot air makes metal move."

"Oh."

He nodded confidently.

"That makes way more sense."

Honestly—

Explaining engineering concepts to someone born in a medieval fantasy world was exhausting.

Still, the potential of steam power made my heart race every time I thought about it.

Continuous mechanical movement.

Industrial machinery.

Eventually locomotives.

Factories.

Pumps.

Vehicles.

A steam engine would change everything.

There was just one problem.

We couldn’t make one yet.

Because while bloomeries produced solid steel blooms—

I needed molten iron.

Large quantities of it.

And for that—

We needed a blast furnace.

I slowly stared down at my sketches while ideas formed rapidly in my head.

A taller furnace.

Stronger airflow.

Higher internal temperatures.

Continuous operation.

If built properly, it could produce pig iron hot enough to melt completely.

From there, casting complex components would become possible.

Gears.

Cylinders.

Pipes.

Engine parts.

The foundation of real industrial machinery.

Finn watched me sketch rapidly across several pages.

"...You’re doing the scary thinking thing again."

"I need a blast furnace."

Finn blinked.

"...That sounds dangerous."

"It absolutely is."

"Fantastic."

For the rest of the day, I barely moved from the worktable.

Sketch after sketch filled the pages.

Internal chamber designs.

Air intake systems.

Stone layering.

Heat insulation methods.

Charcoal consumption estimates.

Meanwhile, Finn occasionally glanced over my shoulder looking increasingly concerned.

"You’re planning something terrible, aren’t you?"

"Revolutionary."

"That’s somehow worse."

Outside, snow continued falling across the clearing while the bloomeries roared steadily in the distance.

And as I continued sketching designs late into the evening—

I realized something.

Steel had only been the beginning.

Because now—

For the first time—

I was no longer just improving materials.

I was preparing to create machines.

The workshop remained illuminated long after sunset.

Pages covered in sketches, calculations, and notes were scattered across the worktable while the sound of scratching charcoal echoed softly through the room.

Finn sat nearby half asleep in a chair while Potato somehow stood outside the window staring directly at us like an ominous forest spirit.

Honestly—

That horse disturbed me sometimes.

Meanwhile, I remained completely focused on the final sketch in front of me.

The blast furnace.

After hours of redesigning proportions and airflow systems, I finally placed the charcoal pencil down.

Done.

I leaned back slightly and stared at the design.

The structure would stand far taller than the bloomeries we currently used. A reinforced stone tower lined internally with heat-resistant clay would allow far higher temperatures and longer operation times.

Most importantly—

The continuous airflow from the waterwheel-powered bellows would let us maintain temperatures high enough to fully melt iron.

Molten iron.

Actual liquid metal.

Once we reached that stage, everything changed.

Casting.

Precision parts.

Large-scale production.

Real machinery.

A slow grin spread across my face.

Finn noticed immediately.

"...That smile always means danger."

"It means progress."

"Same thing."

I ignored him and grabbed another sheet before quickly writing down everything we needed.

Stone.

Clay.

Iron bands.

Large amounts of charcoal.

Sand.

More metal piping.

Stronger tools.

Heat-resistant brick if possible.

And an absurd amount of labor.

Honestly—

This thing was going to be gigantic compared to our current setup.

Finn watched me finish the list before sighing dramatically.

"Please tell me this project won’t almost kill us again."

"It probably will."

"Fantastic."

I handed him the material list.

Finn stared down at the paper silently for several seconds.

"...This is expensive."

"Good thing we’re rich now."

That part still felt strange to think about.

A couple months ago I had been a powerless noble failure with no future.

Now?

I secretly owned a growing steel business hidden in the woods.

Life was weird.

Finn continued scanning the list nervously.

"...Why do we need this much stone?"

"The furnace has to withstand extreme temperatures."

"...And this much charcoal?"

"Extreme heat."

"...And the pipes?"

I paused briefly.

"...Steam."

Finn immediately lowered the paper.

"No."

"Yes."

"No more explaining steam things."

"You need to learn eventually."

"I absolutely do not."

I smirked slightly before standing and stretching my arms.

Outside, snow continued falling heavily across the clearing while the waterwheels turned steadily beside the frozen river.

The bloomeries still roared in the background like mechanical beasts breathing fire into the winter night.

And somehow—

This entire industrial operation was being run by two thirteen-year-olds.

That felt slightly ridiculous.

I grabbed my coat before heading toward the door.

"I’m going home," I said while pulling the hood over my head.

Finn looked up from the materials list.

"...You’re leaving me with this?"

"You’re buying the supplies tomorrow."

Finn stared at the paper again like it had personally betrayed him.

"There’s enough stuff here to build a castle."

"Then hurry."

"I hate you."

"You say that every day."

"Because every day you invent something worse."

I opened the workshop door and freezing air immediately swept inside.

Before leaving, I glanced back toward the sketches spread across the table.

The blast furnace.

The steam engine.

The future.

Bit by bit—

It was all becoming real.

Finn suddenly spoke again as I stepped outside.

"...Hey Leon."

I looked back.

Finn held up the materials list with a deeply concerned expression.

"If this explodes, I’m haunting you."

I laughed slightly.

"Fair enough."

Then, with snow crunching beneath my boots, I began walking back toward the manor beneath the cold winter sky.

By the time I arrived back at the manor, the sky had already darkened completely.

Snow clung to my boots and coat while freezing air followed me through the front entrance as I stepped inside.

Warmth immediately washed over me.

Honestly—

After spending all day around furnaces and snow-covered forests, the manor almost felt too comfortable.

A couple servants greeted me as I walked through the halls before quickly hurrying off again.

Probably because I looked terrible.

My clothes were covered in soot, dirt, and ash while my hands were rough from working metal and stone all day.

I definitely no longer looked like a noble.

As I stepped further inside, I spotted my mother standing near one of the hallways speaking with a servant.

The moment she noticed me—

A strange smirk appeared on her face.

I slowed slightly.

"...What?"

She immediately shook her head innocently.

"Nothing."

That response alone instantly made me suspicious.

"...Mom."

"Yes?," she replied while trying—and failing—to hide her amusement.

I narrowed my eyes.

"What happened?"

"Nothing at all," she replied far too quickly. "You should probably go clean yourself up though."

Now I was definitely suspicious.

Still, I was too exhausted to deal with whatever weird noble nonsense this was.

So after giving her one last confused look, I headed toward my room.

The hallway felt strangely quiet.

Almost too quiet.

I reached my door and pushed it open.

Then froze.

Lilith stood inside my room.

And judging by the expression on her face—

She was angry.

Very angry.

Her deep purple eyes locked directly onto mine while her arms remained crossed tightly against her chest.

It was kind of terrifying.

"...Lilith?"

The moment she heard my voice, her expression sharpened further.

"Where have you been all day?"

Ah.

That explained my mother’s smirk.

I slowly closed the door behind me.

"...Outside?"

"That is not an answer."

She stepped closer immediately.

"Your mother told me you left the manor before sunrise," she said accusingly. "Then disappeared the entire day ."

How long had she been here?

I blinked slightly.

"...When did you arrive?"

"This morning."

Right.

Winter.

She said she’d return during winter break.

I had completely forgotten because I’d been too busy attempting to kickstart the industrial revolution.

Lilith continued staring at me intensely.

"You’ve been avoiding everyone."

"I’ve been busy."

"With what?"

My brain immediately activated every defense mechanism possible.

"Reading."

Lilith stared at me blankly.

"...You smell like smoke."

"...Aggressive reading."

She narrowed her eyes.

Honestly—

Lying to Lilith felt weirdly difficult sometimes.

Mostly because she looked at me like she was trying to dissect my soul.

She stepped even closer until she was only a short distance away.

"I haven’t seen you for months," she muttered quietly. "And now you spend every day sneaking away somewhere."

I paused slightly.

Wait.

Was she actually upset?

Before I could answer, Lilith suddenly grabbed my sleeve tightly.

"...Did something happen?"

The anger in her voice had weakened slightly.

Now she just sounded worried.

I looked down at her for a moment before sighing softly.

"Nothing bad happened."

"That’s not convincing."

"It’s true."

Lilith remained silent for several seconds before finally looking away slightly.

"...You didn’t even send me a letter."

Right.

That.

In hindsight—

I probably should’ve done that.

Instead, I’d spent the last several months building bloomeries, experimenting with steel production, and literally creating giant piles of decomposing manure in the forest.

Not exactly romantic correspondence.

"...Sorry," I admitted quietly.

Lilith looked back at me immediately.

The irritation on her face weakened slightly after hearing that.

Still—

She clearly wasn’t fully satisfied.

"...What are you hiding from me?" she asked softly.

Panic.

Industrial panic.

Because there was absolutely no way I could explain any of this normally.

"Oh yes Lilith, I’ve been secretly building primitive industrial infrastructure in the woods to reinvent modern engineering."

That would sound insane.

So instead I awkwardly scratched my cheek.

"...It’s complicated."

Lilith stared at me for a long moment.

Then suddenly—

She stepped forward and wrapped her arms around me tightly.

I froze.

"You worried me," she mumbled quietly against my chest.

My brain stopped functioning briefly.

Because honestly—

No matter how long I knew Lilith—

Moments like this still completely caught me off guard.