Chapter 1
Prologue
Mysteries are like poison.
A poison that invades people.
Humans have solved all sorts of mysteries using the power of science.
From the mechanisms behind natural phenomena like lightning, to the nature of diseases, and even the distance to the lights shining beyond the sky.
Yet, new mysteries continue to emerge.
We must never give up on unraveling them.
We must never accept mysteries as just mysteries.
If we do, human evolution will halt.
Mysteries, like a wavering veil covering the truth, have the power to devolve humanity.
Sometimes, they even regress humans to monsters.
I, Yosuke Mazekawa, have witnessed such tragedies repeatedly.
The city at dusk always had a somewhat buoyant atmosphere.
People returning home from work or school seemed oddly cheerful, despite likely being tired.
It was as if their day started right at this moment.
Businessmen ducked into bars, while groups of students were drawn into karaoke joints.
To me, someone raised in the countryside, these scenes still struck me as fresh and new.
Where did all this energy come from?
I was walking through the crowd, envying them deeply, when the young girl beside me spoke up.
Yosuke, is something wrong?
I sighed.
Nothing really . . . I was just thinking how noisy the city is.
As I spoke, I turned to her.
Our eyes met. Hers were tinged with red—innocent and adorable like those of a cat.
Her glossy lips and wide eyes exuded a charming innocence.
While her naturally light hair, bathed in the sunset, shone a brilliant crimson.
With a petite face and an alluring figure, her long, slender legs caught the attention of passersby as she walked.
Objectively speaking, she was undeniably a beauty.
But, having a companion who attracted so much attention offered me no benefits.
Most people who saw her stopped in their tracks, increasing the likelihood that we would accidentally bump into them, so I had to dodge hurriedly each time.
Unaware of the impact she had, she stared at me with a broad smile.
Maybe you're missing home? Want to go back?
Her voice was filled with anticipation.
No, that's not it.
Hmm . . .
Yuhi, if you want to go back, then go by yourself.
I spoke a little harshly now to my younger sister, Yuhi Mazekawa.
Why do you have to be so mean? I went through the trouble to transfer to a high school in Tokyo just to be with you.
She puffed her cheeks in frustration.
It was a charming gesture, but I was indifferent to it.
I never asked for you to do that.
But you do need me, right? You'd never survive on your own. You have no life skills.
. . .
I couldn't argue with that.
Without my sister barging in daily to help, I would have absolutely no hope at eating proper meals or keeping any kind of daily routine.
Besides, you need an assistant for your duties. Who else could you rely on if not me?
. . .
She interpreted my silence as agreement.
Right? I'm the only family you have on your side.
You say that like it's a good thing.
Yuhi grinned unabashedly at me, and I could only sigh in response.
Because it is. Anything's enjoyable if I'm doing it with you. Even these duties of yours. Oh, look, there’s the scene of the incident. I'll do my best to help out.
Yuhi pointed to a dimly lit street sandwiched between tall buildings.
The path was even narrower due to bicycles left haphazardly along both sides.
The Sickle Weasel Incident, huh?
I muttered the name of the case I had to resolve as part of my duties.
Right! So, what's a Sickle Weasel again?
Hey, assistant.
Hmm?
I motioned for her to come listen to me. She didn't even understand the basics, and had her head tilted in confusion.
Resigned, I decided to explain it in simple terms.
A Sickle Weasel is a type of spirit that inflicts sharp cuts on those it encounters. In modern times, it’s thought that such injuries might be caused by vacuums or whirlwinds lifting debris, and many consider it a natural phenomenon.