Halo City
I couldn't even spare the attention to blink.
Buried in the thick scent of ink, I moved my pen in a trance. How about this? No. Then what if I do it this way? Still not right. This approach? Not bad.
The moment one calculation finished, the verification of it followed. If the result had come out differently from what I intended, why had it turned out that way?
A simple mistake? Or was something wrong from the foundation up? Before I knew it, I was sweeping the hair that had spilled down over my shoulder.
At last, a finish line appeared in the march of equations that had seemed endless. After tidying the papers, I reviewed everything once more from beginning to end.
There was not a single logical contradiction. Confirming that every equation formed one complete whole, I thrust both arms high into the air.
"I did it! I finally did it!"
My eyes were bleary and my body heavy from days of going without sleep, but my chest swelled and a tingling ran through the crown of my head, and the thought of sleeping never even crossed my mind.
I wanted to tell someone this news at once. Half out of my mind from sleep deprivation and dopamine, I burst out of the reading room and went straight to find Cheshire.
"Cheshire! I finally finished it! I completed the time-travel spell!"
"Congratulations, Mistress Witch… mmmph, mmmph-mmph!"
"You have no idea how hard I worked just to make this one spell!"
"I'm being crushed! Crushed!"
I simply could not contain my joy. Barefoot and still in my nightclothes, I had barreled out and scooped Cheshire into my arms with everything I had.
Cheshire's delicate body made an ominous sound as it was squeezed, but since Cheshire was a formless shadow spirit anyway, there was nothing to worry about.
I bounced in place and spun in circles for quite a while, and only when my mood finally settled did I eat the meal I had been putting off for days.
After practically shoving meat into my mouth, I didn't fight the sudden wave of drowsiness; I curled up on the sofa and took a nap as well.
The moment my head touched down I was out, and when I opened my eyes again it was late at night. Checking the time, I realized I had slept a full sixteen hours.
Had I slept that long even once recently? With my condition restored to perfection, I finally washed thoroughly and leisurely had tea and a snack.
"Congratulations, Mistress Witch. A triumph nearly two months in the making."
"I had a tenfold time acceleration on the reading room, so subjectively it was a year and a half… but thank you anyway."
Needless to say, creating a time-travel spell had never been an easy journey.
At a glance, magic might seem like a convenient miracle that turns imagination into reality. But magic was closer to an act of drawing meaningful possibilities into reality through mana.
In short, you could make a peach tree bear peaches even out of season, but you could not make a peach tree bear apples. There were clear limits that kept it from being called omnipotent.
As I mumbled that around a mouthful of cookie, Cheshire, who had been listening attentively, lifted its tail high and asked,
"Then doesn't that mean a time-travel spell shouldn't be possible either? Crossing through time is impossible, isn't it?"
"That's not quite how it works. Traveling to the future is, surprisingly, within the realm of the possible."
Travel to the past was another matter, but travel to the future was not theoretically impossible.
You could warp spacetime with intense gravity so that one second here became a year outside. Or freeze every cell without damage and thaw safely in the distant future.
Of course, those were one-way trips with no return to the past—essentially no different from dying in this era.
So the time-travel spell I needed to create had to reach the future and still be able to come back to the present. Without that, it was meaningless.
"And at last I found the answer. It's light."
"E-excuse me?"
"Light doesn't experience time. I created a spell that turns an object into starlight. Apply that to myself, and I can pass freely between future and present. That is the absolute core of the time-travel spell!"
"A spell like that… I never even imagined it."
But turning the body into starlight alone was not enough to grant the nature of traveling through the future. Stars had the quality of always remaining in place, unchanging.
So how was I supposed to move between present and future? Wrestling with that new problem, I luckily found a breakthrough.
"Cheshire, do you know what a comet is?"
"Yes. A star that streaks across the sky… right?"
"Mm. They call them tailed stars too, because of the long trails. Comets have one special trait: they have periods."
Unlike similar celestial bodies—shooting stars, meteors—comets appeared and vanished from the night sky on a cycle.
That period might be ten years, twenty, or even longer. For someone who needed to reach the far future, it was an excellent guide.
Cheshire seemed to follow without much trouble, listening thoughtfully before lifting its head as if something had occurred to it.
"Then any comet will do?"
"I'd like to visit as distant an era as possible… so a comet with a period of a hundred years or more would be ideal."
"A hundred-year period… does such a comet even exist?"
"Heh heh heh. As a matter of fact, I've had my eye on one."
I opened a subspace and took out a worn book I had stashed inside—an ancient volume gifted by an old kingdom in the eastern continent.
It recorded that, centuries ago, a dazzling light had hung in the night sky for hours and terrified the king.
A meteor would have flashed and vanished in an instant. No matter how you turned that record over, it was unmistakably a comet.
On top of that, a spell that predicted the movements of the night sky had picked up an enormous comet. It had to be the same one.
"A comet with a period measured in centuries… I really can't resist this…."
"Mistress Witch. Your expression is dangerous."
"Just how many books will have piled up hundreds of years from now? Eheh, ehihihi…."
"Please maintain some dignity…!"
The time-travel spell itself was complete. All that remained was to actually use it.
The comet I would use as a guide was due to appear soon as well. One last test to make sure nothing would go wrong when I cast it.
Practicing before the real thing, I soon ran into a serious problem.
"This is bad. This spell… is way too hard."
The issue was simple: the time-travel spell was so complex that even casting it was a strain.
Honestly, I had never once struggled to use magic. The body I had been reborn into performed like a high-end computer. No matter how intricate or finicky a spell, I found the knack quickly and handled it without trouble.
But the time-travel spell was taxing even for me. It felt like calculating every stage of a spaceship punching through atmosphere entirely in my head. Frankly, I wanted to throw up.
I would need three of me just to cast this—and that wasn't happening. So should I give up and stop here?
No. Thankfully, I already had an idea for solving exactly this problem.
"That thing I've been thinking about for a while—this is a good time to make it."
Its name: the Magic Wand. A kind of high-performance calculator fitted with mana-conductive materials and a specialized computation device.
I had never felt the need to go to the trouble of making one, since ordinary calculations I could do comfortably in my head.
But now the math felt crushing, and I happened to have materials from a secret realm that would help. I set to work at once.
Into crystal wood that conducted mana beautifully I set strands of my own hair, heavy with star mana, and carved out a computation device as if etching semiconductor circuits.
With this, no matter how complex or difficult the spell, I would be able to realize it easily—at least until the computation device broke!
Of course, building that device had cost nearly three months inside the reading room. Outside, only about ten days had passed, so it was fine.
The spell was finished, the wand was ready, and the timing was right. Perfect. Every preparation was complete!
While I waited for the comet to arrive, Cheshire approached with a worried look and asked,
"Mistress Witch. Are you truly all right not sending word that you'll be away only briefly?"
"Hmm? It should be fine. No matter how long I stay there, the moment I return will be right after I cast the spell. Leaving a message would probably just make people more anxious, wouldn't it?"
"There's always the possibility of something going wrong. An error of a week or a month…."
"It's fine. What could go wrong just because I'm gone for a little while?"
If my calculations were correct, there would be no time difference before and after leaving for the future and coming back. Suggesting I might vanish for a bit would only create unnecessary worry.
I told Cheshire it would be all right and stroked its back to soothe it. Cheshire's cat-form back was soft, and petting it was addictive.
Then, beyond the open window, a brilliant comet began to streak across the night sky. The comet's mana hit me in an instant. With a thoroughly serious expression, I warned Cheshire.
"Cheshire, stay as close to my body as you can. One wrong move and you could become a lost child of time."
"Huk… I'll be careful!"
"Good. Then… I'll begin."
I felt no fear that I might fail. I had run the simulation again and again.
Wand in hand, I shared the calculations with it and stacked the structure of the spell in sequence, as if raising a precise building.
The interior of the library filled with so much mana that I could no longer see, and every cell of my body became one with the world.
At the moment I cast off matter and mass and reached the domain of light, with mana at perfect fullness, I spoke the spell's incantation.
"Aether Temporius!"
⟨ Time-Travel Spell ⟩
A spell for traveling through time.
With a powerful light that punched through the library's ceiling, my consciousness touched somewhere beyond spacetime, and every sensation of the body vanished.
Success. I knew instinctively that the spell had manifested perfectly. The senses that had slipped from my grasp returned once more.
Regaining control of my body, I slowly opened my eyes—and the sight that filled them forced a gasp of pure astonishment.
What… is this….
The first thing that entered my vision was a skyscraper that seemed to pierce the heavens. Next came the dazzling neon signs that banished the night's darkness. Then the airships gliding here and there, and the enormous electronic billboards that seized the eye.
For a moment I wondered whether I had not come to the future at all, but crossed into the world I had lived in before reincarnation—the landscape was that familiar.
But the shock lasted only a moment. Something felt wrong about the view. Why could I see the entire city at a glance?
The instant I registered that fact, my balance pitched wildly. Then came the sensation of being yanked downward, and I plummeted endlessly toward the ground.
"Huh? W-wait…!"
"Mistress Witchhhhh!"
Yes. The place I occupied was none other than several kilometers of open sky, far above the ground.
The sensation of bungee jumping without a cord. My heart lurched at being flung out without any mental preparation, but I soon recovered my composure.
I had a spell for flying through the sky. As long as I could cast it before I hit the ground, there would be no problem.
I first pulled the screaming Cheshire into my arms. Then I swung the Magic Wand I still held and shaped the spell.
"Cadere! …Huh? Cadere! Cadere!"
Strangely, the flight spell would not activate at all. It felt as if some vital pump inside my body had broken. Only then did the sense of crisis drain the color from my face.
If I slammed into the ground like this, even I would not walk away intact. The absurd kinetic energy would turn me into a bloody pulp no one could bear to look at.
Only a few seconds remained before I hit the ground. Not a single failure could be allowed. Instinctively I swung a simple spell with no chance of failure.
"Repulsio!"
A spell that repelled kinetic shock. I wrenched every scrap of mana from my body and drove that spell hard toward the ground.
KRA-BOOOOM! The rebound of tremendous kinetic energy. It collided with the floor, and with a roar it cracked a small crater into the pavement.
Fortunately it was an empty back alley, so no one was caught in it and I reached the ground safely—but the shock had left my legs weak.
"I-I thought I was going to die…."
"Meow…."
Holding Cheshire—who had lost the ability to speak human words—in my arms for whatever comfort it offered, I gasped for breath and pressed a hand to my chest.
This hadn't been the plan. The first moment of time travel was too undignified to watch with open eyes.