Maxwell's Demon
“Nnngh...”
It felt like I was drifting through a deep dream.
What the hell had I even been doing?
“Ugh...”
A sudden wave of pain crashed over me, and I curled in on myself.
Had something punched straight through my gut?
No. I hated this.
I hated pain...
“Hey. If you’re done sleeping, how about getting up?”
A familiar voice.
My savior.
My one and only master.
The reason I kept living.
The idol who had let me keep my mind intact through hundreds of regressions.
“Huh?”
The woman finally registered the situation and tried to sit up.
But her arms were bound, so she couldn’t properly push herself upright.
“Ugh, what is this...”
“You’re awake. Took you longer than I expected—I was starting to get pretty worried.”
“S-Seo-hyun-nim...? N-no, Seo-hyun?”
She thrashed and wriggled, trying to rise.
But I had her pinned firmly from above, so she couldn’t budge an inch.
“As expected. Without the pocket watch, you’re no different from an ordinary person.”
“W-what? W-wait a second...! When did you even—!”
I dangled the pocket watch in front of her face, swinging it slowly left and right.
Her eyes followed the swaying watch, and somehow the sight made her look pitiful.
“Um...”
“W-what is it?! E-even so, this is moving way too fast...!”
“What are you even talking about? Never mind that. I’ve got a few questions.”
I flipped the pocket watch over and showed her the back.
“W-why are you...”
“Right here on the back—Maxwell. Who engraved this? I looked around, and no brand sells a pocket watch shaped like this.”
“Th-that’s...”
She hesitated for a moment, then squeezed her eyes shut.
“Someone precious to me... made it by hand.”
“Someone precious?”
“...”
“Well, fine. Next question. This watch doesn’t seem like an ordinary pocket watch.”
“...I can’t tell you that.”
She seemed to be holding something back.
I got the strong sense that she was still afraid of a future that hadn’t found her yet.
“Alright. I think I get the gist.”
“H-huh? What do you mean, you get it...”
“This is how you use it, right?”
I focused on the pocket watch.
I was only holding it, yet somehow I instinctively knew how to make it work.
Click—
Something opened with a soft sound, and the second hand began to tick backward.
“W-wait. How did you...?”
“Oh, it works.”
The air around us slowly began to freeze.
As the room temperature plummeted in real time, a thin skin of ice formed on the warm milk sitting on the table.
A temperature-dropping ability?
That was my first thought—until the powerful surge of energy that followed made me realize this was something far greater.
“Mana...?”
The inscription on the back of the watch glowed blue and began feeding it mana.
You might assume it came from a simple mana stone, but the sheer volume pouring out of such a tiny pocket watch was absurd.
As if a miniature power plant were sealed inside.
But every power plant needs fuel.
So what exactly was fueling this little pocket watch?
No way...
An unbelievable hypothesis suddenly struck me.
“A second-kind perpetual motion machine?”
“...”
Good lord. A perpetual motion machine.
Something I’d only ever seen in science fiction, right here in front of me.
The temperature was dropping so fast that I hurriedly stopped the watch.
The second hand that had been running backward settled back into place, and the chill in the air began to ease as the heater kicked in again.
A second-kind perpetual motion machine is the general term for any perpetual motion device that violates the second law of thermodynamics.
The second law of thermodynamics: the entropy of an isolated system never decreases.
Put simply, entropy is the measure of disorder.
Even if disorder decreases in some local system, from the perspective of the whole it either stays the same or increases.
That same sentence was engraved on the back of the pocket watch—probably carved there by its creator, proud of having built a second-kind perpetual motion machine.
Well, this wasn’t a science lecture, so I’d stick to the essentials.
Anyway, a second-kind perpetual motion machine works like this.
Heat always flows from hot to cold.
It never flows from cold to hot on its own.
But what if you could freely move energy from cold to hot?
You absorb the heat floating in the air, turn it into a power source, and dump the chilled air outside.
Since the amount of air on Earth is practically infinite, you end up with a semi-permanent engine.
No need to shovel coal or mess with dangerous radioactive energy.
You just pull heat from the surroundings whenever you need it.
Heroes and villains with unique abilities are always limited by mana.
When their mana runs dry they can’t use their powers, so they carry mana stones charged with mana—but there’s a hard limit to how much you can store.
With this one pocket watch, that problem vanishes.
Just absorb the ambient heat and use your ability.
It solved one of humanity’s chronic headaches: the eternal shortage of energy.
“So that’s how you were able to draw that much power.”
The technique she had used earlier had been powerful enough to drive off a monster that looked ready to swallow an entire cruise ship in one bite.
Its range rivaled or even surpassed white phosphorus, and the mana woven into it melted monster flesh with terrifying efficiency.
To produce that kind of firepower without a single grain of gunpowder, you’d need someone on the level of Germany’s S-class hero Gustav.
And even if that firepower-obsessed lunatic showed up, I still doubted he could have forced that monster to retreat.
“...It’s not a perfect second-kind perpetual motion machine. It’s broken.”
“Broken?”
“...”
She trailed off mid-sentence, and I sighed.
“Last question.”
“What is it...?”
“Your name isn’t Yeon-woo, is it.”
“...!”
“I did a little digging into your identity. Mother and father are both dead. You’ve got an older brother and a younger sister, but the sister is listed as missing.”
“Th-that doesn’t prove I’m not Yeon-woo...”
“You’re not a guy.”
“Euh...?”
I pointed at her chest.
A bit of loosened compression bandage was poking out from under her clothes.
“W-when did that...”
“My guess is the younger sister is still alive and the older brother is the one who’s missing. Did you steal his identity?”
“S-steal?! I just...!”
She started to say something, then hung her head.
“Just...”
“Forget it. Anyway, I’d like to hear your real name. Can you tell me again?”
“Huh?”
Her eyes went wide at my words.
She hesitated a moment, then let out a sigh and answered.
“Yeona. Like I said, Yeon-woo is my older brother’s name.”
“Yeona... Pretty name.”
“...When we get to the Academy, call me Yeon-woo. I registered under my brother’s identity.”
“What about dorm life?”
“I’m going for a private room, so it’s fine. The top ten percent get their own space.”
“Confident you’ll make the top ten percent, huh.”
Yeona avoided my gaze, then suddenly realized something she’d overlooked and started thrashing her bound hands.
“A-anyway! G-give that back! You’ve already said everything you wanted to say!”
“Hmm. Tempting. I’ve been having a hard time finding a decent power source.”
“W-wait! That was originally mine!”
“Lots of functions. Though the most important one—telling time—doesn’t seem to work. Watching it reverse one second for every second that passes... is there some meaning to that?”
“Th-there’s no special meaning!”
I fiddled with it a bit more and suddenly found a strangely shaped button.
“This is...”
“Euh...?!”
A dial designed for operating the watch, and a uniquely painted black emblem.
Anyone could tell one of the watch’s core functions was sleeping inside.
“Th-that one you really can’t! If you mess with it carelessly...!”
“I’m not going to touch it. Don’t worry. I’ll give it back now.”
“H-huh? Really?”
“Yeah. Not like I know what’s in there. Are you going to tell me the functions?”
“N-no... of course not...”
“Then take it. Feels a little wrong to keep teasing the person who saved the ship, anyway.”
With that, I untied her hands and held out the pocket watch.
The moment she reached out to take it, the compression bandage that had been dangling on the floor snagged on the edge of the bed.
At the same time her body pitched forward, her hand brushed the dial of the pocket watch.
And then.
Tick, tock.
And....
Tick, tock, tick, tock, tick, tock, tick, tock, tick, tock, tick, tock,
And.......
Tick, tock, tick, tock, tick, tock, tick, tock, tick, tock, tick, tock, tick, tock, tick, tock, tick, tock, tick, tock, tick, tock, tick, tock, tick, tock, tick, tock, tick, tock, tick, tock, tick, tock, tick, tock, tick, tock, tick, tock, tick, tock, tick, tock, tick, tock, tick, tock
Time rewound.
When I opened my eyes again, I was standing in the middle of the room.
What... just happened?
Yeona was still lying beneath me, sound asleep—she hadn’t woken yet.
Did she fall back asleep?
Her hands were bound with rope again.
I was sure I’d untied them. How?
“Nnngh...”
Yeona showed signs of waking.
I waited for her to rise, and the moment her eyes finally opened, a strangely familiar voice reached my ears.
“Ugh, what is this...”
“Huh?”
I felt an odd sense of familiarity in her voice.
Déjà vu?
Somehow it was a voice I’d heard before.
“S-Seo-hyun-nim...? N-no, Seo-hyun?”
After hearing Yeona’s second line, I realized something was wrong and checked the clock hanging on the wall.
The clock was pointing exactly ten minutes earlier than the time I had just been in.