What do you mean my cute disciples are Yanderes?

(MC POV)

I was guided by the hand by Odriana and Elaria, both of them leading me through a small passageway that connected my former bedroom to what they dubbed 'The Workshop'.

The passageway had been hidden behind the largest painting that had covered an entire section of a wall back in the room.

I am quite ashamed to report that it was a painting of a younger me wearing an unbuttoned dress shirt and pants, revealing an exaggerated set of abs underneath the shirt. I definitely did not look like that when I was at that depicted age.

I had mixed feelings when my younger sister had skipped towards the drawing of me and started pressing the abs in a pattern, causing a section of the wall near her to open outwards.

Odriana then ushered me through the hidden door, guiding me down a spiral staircase with Elaria following closely behind.

Fluorescent lights blinked on when the wall closed shut behind us, illuminating a long passageway ahead of me.

With Elaria holding on to my left hand and Odriana my right, I was half-dragged, half-carried towards their destination.

"You'll love it Onii-sama! Maybe after seeing everything you'll finally remember!" My little sister declared cheerily.

I really doubt it will be that convenient but I wasn't going to tell her that.

But still… This whole corridor was rather unnerving and I'm already ignoring the fact that fluorescent lamps were inventions way beyond the Renaissance age.

Something tells me my little sister's scope of operations has been much bigger than I had initially thought...

The passageway ended at an unassuming brick wall, its look similar to the rest of the corridor that we were in.

I looked back to see if we might have missed a turn somewhere but there were no gaps in the walls as far as I could tell.

My little sister skipped towards the wall, pulling out one of the bricks to reveal it as a fake cover for a keyhole behind it.

My elder sister sauntered towards the opposite side of the wall at the same time, mimicking Elaria's actions except her side had two levers instead of a keyhole.

Pulling out a key from between her bosom, Elaria stuck the key into the hole and twisted it clockwise.

She glanced towards my Elder sister, "Pull the lever, Kro--Onee-sama!"

Odriana pulled one of the levers down.

Whatever I had expected the lever to do, a metal cage dropping down from the ceiling above me was not one of them.

I barely managed to roll out of the way when the trap crashed down at where I had been, missing me by a mere hairsbreadth. If it wasn't for my current smaller stature, it would have most likely caught me inside.

"Wrong lever!" My younger sister yelled indignantly, fussing over me to check if I was hurt.

"Oh dear… My deepest apologies," My elder sister apologised, pulling the correct lever this time.

There was a soft click and the brick wall in front of us pulled back and away before sliding out of sight.

Compared to the dirt ground of the passageway, the floor behind this hidden door looked metallic and smooth.

The clanking sound it produced when I stepped on it confirmed its metallic properties.

I had no time to inspect the ground any further as I was busy marvelling at the contents of the giant room in front of me.

Did I say giant? I meant humongous. Like, I'm pretty sure this entire underground complex took up the underground space of the entire town in fact.

The room was painted pure white, the walls and floors made up of individual white metallic tiles for what I assumed to allow for better maintenance.

Within was a vast array of electronics and machinery, all of them looking rather crude and ugly though I'd wager that's more because the creator focused more on functionality than making them look pretty.

There was a low humming noise from a big machine in the corner which I could only assume was the generator for this room. How it was made and what it was running on I have no idea.

Wires were connected from it to various machinery in the room, some I recognised and some I didn't.

I pointed to one of the biggest machines in the corner of the room, "Is that… A computer?"

Elaria nodded her head enthusiastically, "As expected of Onii-sama! Sugoi! Your memories are returning right?! I based that thing's design off the ENIAC that you showed me before!"

I most definitely do not remember showing her anything like that. I only guessed what it was since I saw the wires, blinking lights and what looked like a very rudimentary form of a circuit board.

"What is that generator running on then?" I asked.

This time it was my elder sister who answered while patting my head, "Fufufu~ Allow your big sister to explain this one my dear little brother. I'm sure everyone knows that monsters are a menace to everything in this world, yes?"

I shook her hand off my head, "Don't tell me it's as convenient as there being monster cores acting as power sources."

"Oh? Has dear little brother already looked into the Monster Crystals' usage? I expected no less of you, fufufu~"

No, it's because that's the standard for most settings isn't it? It's also the most convenient as well. Put monsters in the world and have them grow cores or something inside their bodies which can be conveniently used as renewable energy sources.

I'd think if humanity really found out about this, they'd already be hunted to extinction within the year.

"Ehehehe~" Elaria giggled. "I spent a good full year to understand the characteristics of the Monster Crystals, but it was all thanks to Onii-sama giving me an idea of other worlds that use them that I can think of such a thing so quickly!"

So it's still because of me huh?

She pulled me towards one of the machines where the corpse of a wolf type monster was laying. The whole setup looked like some sort of butcher's chopping board except it was more gruesome with all the blood-soaked medical tools lying around.

Elaria hopped happily to the table, picking up one of the knives in her hand, "You're just in time Onii-sama! I left this one around to experiment on since the 'An Ney May' Labour division would handle tasks like these. But here! Let me show you!"

Experiments? I must have heard wrong right?

I watched as my little sister plunged the knife into the belly of the corpse without hesitation, cutting it open in one smooth motion.

Holding the incision open with one hand, she plunged her dainty little hand into the corpse, digging through it for a bit before pulling a fist sized, black coloured crystal out. She was entirely unperturbed by the blood drenching her entire arm.

She crouched down and presented the fist sized crystal to me proudly, "Look, look! Elemental Quarks solidifies within monsters to become crystals a few days after their death! After cleaning and processing it, we can use it for power! The bigger the monster, the bigger the crystal! One that is of this size can power a house for a day right now, if only I can improve on the refining process it'll make it last much longer."

I am hesitant to even ask how many corpses she had to go through to refine this process.

Not to mention the fact that usually monsters that are killed would simply be used as food and materials or immediately disposed of to avoid attracting other monsters, probably explains why these 'Monster Crystals' haven't been found by anyone else yet.

"That's good and all…" I said, pushing her bloody hand away with a finger. "I assume you've released every new technology so far out to the public?"

Odriana chuckled, "Oh my dearest little brother really knows how to make jokes! Of course not! We reserve the best ones for ourselves while dribbling the outdated ones to the others and selling them at sky high prices. Once we drain out the nobles and the rich folk, we'll be able to establish ourselves as the head of any future endeavors without competition!"

I looked up at my elder sister with narrowed eyes, "I don't suppose you'll also be making the people reliant on your company's goods to gather support from the masses so no other business can touch you?"

"Ufufufu~ As expected of my most adorable brother to figure all this out! Totally unlike that dumb Dailus who fell right for our scheme to take over the family business~ In fact, we've already achieved that part of the plan already!"

This is beyond frightening…

A little sister that is a genius scientist with little to no morals coupled with an elder sister that is merciless in business… I fear for the future of this world.