("...Um, hi? Can you hear me?") Kotori said.

Unfortunately, the Demon Lord did not respond very favorably. With a sour look on his countenance, he stormed over to his subordinate and shoved the glass jar into Orkruz's pale hands.

"These bottles are broken too," Mephistos insisted. "The spirit inside here isn't fully sealed."

"That's impossible," the long-haired demon replied, crossing his arms. "If the seal were broken, the soul would evaporate immediately."

The robed demon held up the jar in his hands. He stared very intently at the amorphous blob in the bottle, trying to detect any abnormal features. The demon wrinkled his ears, as if trying his hardest to pick up any sound. He also summoned a glowing light to his palm, which illuminated the surface of the glass.

Kotori abruptly went silent. After observing the Demon Lord's negative reaction, she realized that that her speech(?) was an anomaly. If anything, he intended to put her into a dark place where she was fully deprived of all her senses. While this bottle certainly accomplished something very close, her awareness seemed to be a strange ability that still allowed her to observe her surroundings without a physical body. Kotori had no idea whether this ability was commonplace, but she didn't want her vision to be taken away from her.

The fair-skinned demon named Orkruz appeared to be an advisor of the Demon Lord. Kotori reasoned that he was some kind of knowledgeable dark wizard. If her bottle was truly defective, Kotori certainly did not want to be transferred to a different bottle that did its job more effectively. Worst case scenario, he would turn her into the subject for a research experiment. She had read enough dark fantasy in her youth to know that it was never a good idea to end up in an evil wizard's laboratory.

It was best to pretend to be ordinary.

"I don't hear anything," the Dark Wizard said, shaking the bottle slightly near his ear.

Demon Lord Mephistos frowned. 

"I don't detect any magical anomalies with the bottle," Orkruz continued. "Perhaps you imagined it."

"I know what I heard, Orkruz. I did not imagine it."

"It's been a stressful evening. I'm sure you must be upset with losing your pillow."

The Demon Lord's eyes narrowed, and the stray bangs of his coal-black hair obscured the expression in his pupils. He said nothing, and walked forward a few steps until he loomed over the corpse of the undead sheep. As the fires continued to smolder in the background, he stared at the charred remains for several long seconds.

The long-haired demon coughed slightly.

"Do you want the bottle back?" He asked.

There was no response at first.

Mephistos knelt on the ground and hesitantly reached out a hand. The motion seemed uncertain and insecure. However, eventually the Demon Lord brought his palm atop the corpse's forehead. He was delicate and fragile, as if he were afraid that the lamb would crumble to ashes with the slightest bit of force. The expression on his face was hidden in dark shadows.

The Demon Lord muttered something inaudibly under his breath, and the charred homunculus suddenly vanished into thin air with a flash of light.

He remained kneeling on his knees for a few moments thereafter, seemingly lost in his thoughts.

"My Lord?" Dark Wizard Orkruz repeated.

"I heard." Mephistos responded. "Leave me. I need some time for myself."

Orkruz turned around, but then hesitated.

"Are you sure you don't want the bottle? When the Hero arrives... perhaps it would be better if..."

"I don't trust that spirit. The bottle is broken, and the only reasonable culprit for the oddities tonight is that soul. Its identity is unverified. For all we know, it could be a seraph, dragon, or a god. You should look into it if you get a chance, but take precautions if you wish to study it."

The Dark Wizard sighed. "You're being unnecessarily paranoid, Lord Mephistos. This jar would shatter trying to contain anything more powerful than a common wizard. The soul would never fit inside. The things you speak of are impossible."

"I do not trust it in either case," he repeated.

Orkruz sighed again and then dusted off the ashes that had clung to his robes.

"I'll leave it in your office then. Ignore it if you want, or use it as a paperweight."

"Don't expect me to use it."

+ + +

True enough to his words, Kotori was consequently abandoned on the bookshelf in the Demon Lord's office.

She slowly collected a layer of dust over time.

She wasn't sure if this was the best outcome that she could have sought for herself, trapped within a glass bottle inside the Demon Lord's Castle. Optimistically speaking, it was better than being dead, and she was still aware of her surroundings. It certainly wasn't quite the version of a damsel in distress romanticized in trashy adult romance novels that she had occasionally read back on Earth, as her own imprisonment turned out to be mind-numbingly dull.

Kotori couldn't decide which was worse — being ignored by the Demon Lord entirely or being basically raped by a reverse-harem of demons like in some of those X-rated otoge games that she definitely hadn't played as a teenager. In either case, she found it ironic that this setting was essentially identical to one of those isekai novels that were popular in Japan, minus the fact that she had never been hit by Truck-kun. Unless... she had passed out drunk in her apartment bathtub and drowned? ...Ughn... It was slightly too depressing to think about, so Kotori decided to conveniently forget about that possibility. *sweats*

When you weren't sure if Schrödinger's cat was alive or dead, in Kotori's opinion, it was better to disregard the cat entirely. Quantum superposition was dull as heck and she'd prefer not to think of her isekai experience as an analogy to quantum entanglement. The Chinese philosopher Zhuangzi, for instance, famously wrote a parable about man dreaming that he was a butterfly, which is often used as the prototypical dream argument that there is no way to distinguish reality from illusion.

Kotori often found herself thinking in circles, stuffed inside a small bottle.

Days passed...

Then weeks...

Months rolled by...

Fortunately, Kotori's mysterious ability to sense the environment was a real lifesaver when it came to boredom.

She had plenty to time to test out the limits of her awareness. For instance, she learned that there didn't seem to be a precise limit to what she could perceive. The experience was much like looking at the world from the third-person perspective through a pinhole telescope, as it was only possible to focus on one subject at a time. Her peripheral vision was entirely absent.

The main limit appeared to be her concentration. It took substantially more effort to focus on smaller and far away objects, and her eyes(?) started to hurt if she strained for too long. It was also difficult to see through walls and solid objects. Every ten or fifteen minutes, Kotori needed to take a break and sink into complete darkness. 

The Demon Lord's office was very plain. Aside from bookshelves and a desk, it had very few decorations. Most of her days, Kotori spent her energy perusing the bookshelves trying to recognize the strange symbols on the dusty tomes. While she couldn't open any of the books, there were plenty of runes on the spines. She counted 892 unique runes, which seemed to suggest that the demon language likely used a logographic writing system, similar to Japanese kanji or Chinese.

Because she was bored, Kotori counted the frequencies of each character and started memorizing them, even though she had no idea what they meant. She had several educated guesses, of course, since she presumed that certain prepositions like "and" and "to" were especially common in book titles, although she had no way of confirming her suspicions in the beginning.

Kotori also found some ledger sheets on the Demon Lord's desk. They looked somewhat like numbers, so the young university professor amused herself with attempting to decode the numbers based on simple arithmetic. To her disappointment, it was easier than expected and she solved it in less than a day. The demons used a decimal (base-10) numeral system, which made it easy for her. A hexadecimal or octal numeral system would have excited Kotori more, simply because she was so bored that the added challenge would have entertained her for longer.

The other oddity about the Demon Lord's office was the window. 

There was one small rectangular window on the far wall. It faced the sky and was the primary source of natural light for the office. It grew gradually brighter at some times of the days and dimmer during the night. 

This in itself was not that unusual, however Kotori was an astute observer. The light from the window always casted two shadows, implying that there were two moving light sources in the sky (two suns?). Binary stars were a phenomenon in her former universe, so this wasn't too strange, except that some quirks of the shadows concerned her. The angle between the shadows never changed, and always remained constant at ~30 degrees. Under her limited knowledge of planetary motion, this type of arrangement was virtually impossible, as the hypothetical planetary orbit would be unstable. There were only a limited number of Lagrangian points in a three-body problem, and the 30 degree orientation was not one of the stable solutions.

Saikawa Kotori was far more troubled by this observation than she wished to admit. Although the angle of the shadows was such a trivial detail, it was inconsistent with a heliocentric view of the universe. It made her question everything that she knew — whether the science she had spent the first half of her lifetime studying on Earth was even relevant in this world. Of course she had observed some phenomena that appeared to be "magic" upon arriving here, but she had been hoping that certain laws of physics would remain consistent.

Conservation of momentum?

First law of thermodynamics?

Maxwell's equations?

She couldn't really assume any of these things were true anymore, and it left her feeling anxious and even depressed. If science were a religion, the revelation that perhaps none of these principles were true was almost equivalent to telling a pastor that God is dead. Kotori felt unstable and queasy thinking about it.

+ + +

Kotori's existential melancholy aside, the main highlight of her days in captivity was seeing the Demon Lord.

Perhaps it was twisted (Stockholm Syndrome?), but Kotori was perfectly self-aware of her situation. From the start, she just couldn't bring herself to hate the Demon Lord. He had never wanted her here, and Kotori had randomly fallen out of the sky. Neither parties wished to be in this awkward quandary, and Kotori believed that the horned man had acted fairly understandably. It made total sense for the dictator of a kingdom to be distrustful of a stranger in his bedroom, and it was a happy(?) accident that Kotori hadn't been killed straight away.

At the very least, he didn't seem to ooze evil like certain fictional stereotypes she had been familiar with.

As the months passed, she had an ample amount of time to observe the Demon Lord in silence.

In her honest opinion, he seemed to be a normal man. He did paperwork, got frustrated at times, and paced around his office. Sometimes he talked to his grotesquely-shaped subordinates in his office or made magical(?) telephone calls from this unfamiliar device that looked like a conch shell.

Kotori looked forward to the time when Demon Lord Mephistos was in his office, because it meant that she could snoop around at the papers that he shifted around. Occasionally, he read aloud some of the documents, which meant that Kotori could pick up one or two new characters in her vocabulary. Slowly, over time, Kotori pieced together a scattered framework about the world that she arrived in.

The main concern about the Demon Lord was that he seemed progressively more irritable as the months passed. 

In the beginning, the Demon Lord was amicable and efficient with his paperwork. He was polite and friendly to his minions, and he even laughed with some of his advisors. However, as the days stretched into weeks, bags formed underneath his eyes. He started to look miserable and his sclera went bloodshot. After the first month, Demon Lord Mephistos became a rabid wolf that easily lost his temper. He snarled at anyone who disagreed with him.

His productivity dropped, and Kotori would often see him coming to the office at odd hours in the night. He would sit down, fidget, write a few words, and then get up and pace maddeningly around the room. It got worse with every passing week, and the pile of unfinished paperwork steadily grew to several large stacks. The office grew progressively messier, until the floor was littered with crumpled sheets of paper and shredded books that the Demon Lord ripped apart with his claws when he was particularly frustrated.

The violent behavior only worsened with each day, and Demon Lord Mephistos picked up a nasty hobby of torturing small animals that the servants caught for him. He would throw the carcasses out the window after cutting them open, retying the organs together in odd configurations, and pumping them full of dangerous-looking chemical substances. A few times he snapped and roasted some poor orc minions alive. Occasionally, he would burst out in diabolical laughter and start talking to himself like he heard imaginary voices in his head. He would also give his demon generals extremely unreasonable commands like stealing an Emperor's firstborn child, flaying it, and mounting it on a pike.

The diagnosis?

Obviously, it was sleep deprivation.

The Demon Lord was an insomniac, and he hadn't slept at all since the day Kotori first arrived.

Saikawa Kotori's mounting concern and worry grew with each passing day. 

...Until one evening, nearly 9 months later, the Demon Lord stumbled into the office covered in guts, slashes, and gore.

He was missing an entire arm and a massive chunk of his abdomen.

A large golden falchion was impaled in his back.

∎

ohko

I'm sorry if I totally geeked out and lost everyone's attention in the nerd sections... if it was really bad, please let me know and I'll definitely hold back in the future.