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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.
You sure know a lot about spirits. But I guess that's what you get when you study folklore in college.
No, this is pretty much common knowledge. Anyway, similar incidents have been frequently happening on that street.
A lot of people have been injured then?
I noded in response to Yuhi's question.
Yes, for the past three months, several people passing through this street have sustained cuts without any contact with those bicycles or anything else. They just feel a sudden pain while walking down the middle of the road, and then notice the wounds.
Yuhi tilted her head curiously as she listened to my explanation.
Hmm? But isn't it possible that this happens due to a natural phenomenon?
The idea of a natural phenomenon mimicking the behavior of Sickle Weasels is highly dubious. Even if a vacuum were to occur, human skin does not tear easily, and it is rare for flying debris, such as sand or small stones, to cause such cuts. At the very least, it seems unlikely to result in over ten cases within three months.
Huh? So if it’s not a natural phenomenon, then does that mean a spirit is behind it?
I grimaced at Yuhi's words.
Such ideas are why this case is turning into an urban legend. Thanks to that, my afternoon plans are completely messed up.
Did you have something else to do?
I wanted to go home and sleep.
Your duties seem more meaningful than that.
Ignoring her comment, I stepped into the scene of the incident.
Hey, be careful!
Startled, I gestured to stop Yuhi as she tried to step forward.
No need to worry. Since the rumors have spread on social media, no incidents have occurred. The culprit must be wary and has stopped acting. But even without new incidents, the rumors continue to spread.
I sighed deeply.
Really . . . it's because people believe in spirits that these troublesome accidents just keep increasing.
Why would anyone think such things exist?
They’ve never even seen them.
The culprit . . . are you saying there’s a person behind this incident?
Yuhi frowned, and I nodded in agreement.
Of course. The Sickle Weasel, along with other spirits—these so-called 'monsters'—does not actually exist.
Having said that, I began observing the scene.
This area, being at the back of a building, had neither windows nor service entrances. The only noticeable things were abandoned bicycles and trash strewn on the asphalt.
Ah . . . the path ahead grows even narrower. There's a wider road right beside us, so no one would usually pass through here, right?
Yuhi muttered, looking ahead at the path.
Right. Structurally, it doesn't even function as a shortcut. That's probably why it's become a hotspot for abandoned bicycles.
So, it means people mostly come here to leave their bicycles? Maybe whatever is happening here is intended as a punishment for those doing wrong?
I shook my head.
No, if that were the case, the victims wouldn't be so specifically targeted.
What do you mean?
The majority of the victims are women—all of whom have sustained injuries to their legs.
As I recited the memorized case data, Yuhi looked at me, surprised.
Ah . . . that does seem odd.
The incidents also seem to occur at the same time of day, from evening through the night. With such a bias, certain patterns started to emerge.
Yuhi gave me a look of anticipation.
Have you already figured out the culprit?
I had a rough idea of the culprit's profile after reviewing the case information. I've asked Division Six to sift through potential suspects. We're here to find evidence.
I checked each abandoned bicycle and scrutinized anything that was scattered around.
Hmm. By Division Six, you mean that police lady who keeps bothering you, right? You should rely on me instead!
Though my sister pouted, I ignored her and continued the investigation.
It had been about a week since the last incident, but there was still a chance evidence remained.
Solving the mystery required a key.
Mere speculation wouldn't suffice.
Without evidence, any theory would be unpersuasive.
If we can't find anything concrete here, we'll have to look for evidence from a different angle.
Then, all of a sudden, I found what we were looking for and let out a sigh of relief.
Yosuke? Did you find something?
Yes, let's head to the suspect's place now. I'll have Division Six make the arrangements.
Division Six again? Hey, when's it going to be my turn?
Yuhi wore a dissatisfied look on her face.
Without paying any heed, I pulled out my cell phone and contacted the person who had requested our help.
As I opened the front door, an unpleasant odor wafted toward us.
Tied-up trash bags lined the hallway, and I could see plastic bottles scattered in the back room.
Ugh, what a messy room!
Yuhi grimaced.
I couldn't bring myself to look down on the occupant of the room, though.
If Yuhi hadn't been meddlesomely helping me, my room would probably be in a similar state.
Excuse us! There was no answer, so we just borrowed a key to open the door.
Yuhi called out as she headed further inside.
Nobody home, I guess? The lights are on, though.
We'll find out once we're inside.
I stepped into the room.
Ah, be careful! Don't go ahead alone!
Yuhi hurriedly followed behind, flustered.
We were in a one-room apartment near the site of the Sickle Weasel Incident.
Without needing to search, we found the apartment's owner on the bed.
A man about my age was huddled up, clutching his head.
He was facing down, his arms covering his ears, unaware of our presence.
The bed creaked faintly.
The man was gripping the bed's rails and shaking.
It was as if he were frightened by something.
Excuse me!
There was no response.
Hey, we're coming in!
Thinking it was futile to wait, Yuhi approached him and lightly tapped his shoulder.
Ah . . .
The man let out a faint noise and looked up.
Huh?! Whoa! What do you want?!
His voice was filled with panic, and he backed up until he hit the wall.
It was a natural reaction, all things considered.
We rang the bell but got no response, so we let ourselves in.
What do you mean, let yourselves i—
I sharply cut him off as he attempted to yell.
We have special authorization from a public agency.
Knowing it was impossible to fully convince him under these circumstances, I unilaterally declared our position to crush any immediate objections.
My big brother and I are external collaborators with the police. Sort of like detectives, one might say.
Yuhi stood by my side, facing him.
Detectives?
The man frowned.
Teppei Ueki, twenty-two years old, a third-year university student. You've taken on part-time work recruited by the Urban Development Department's Parks Division, cleaning around the fountain plaza in front of the station on four evenings a week. The job also included tidying up and removing abandoned bicycles.
I stated his profile matter-of-factly.
And what about it?
There's a narrow alley lined with abandoned bicycles in your area. Are you aware of the incidents occurring there—people getting hurt without an apparent cause?
. . . Oh, yeah. Something about a Sickle Weasel spirit, I think . . .
Though his expression tensed, the man nodded.
Right, these incidents are rumored to be the work of a Sickle Weasel. But they occur too frequently to be a natural phenomenon, and of course, they aren't the work of any spirit.
. . .
The man fell silent.
But assuming someone rigged the scene, we encounter a problem. Very few people use that alley as a pathway, but quite a few come to leave their bikes there. It’s possible that someone could have accidentally witnessed the setup.
I continued explaining how we traced our way to him.
However, no one suspects a man in a conspicuous work uniform tidying up bicycles. People who come to drop off their bikes just turn around if they see a worker.
This was something we understood before even arriving at the scene.
The narrowing down of suspects had long been completed.
And you emerged as a prime suspect. You were invariably scheduled around the time of the incidents.
The man swallowed nervously, then glared at me.
So, you're saying I'm suspicious?
Yes, you are the culprit—not some Sickle Weasel spirit.
Ha . . . ?!
Then, the man’s face twisted into a strained smile, and he looked down.
His shoulders trembled.
Sickle Weasel spirit . . . Haha . . . Yeah, right . . . That's impossible. There's no way, I'm different . . . I must be different . . . I am . . .
A breeze softly blew through the room, despite the windows and entrance door being closed, and with no air conditioner running.
It was an impossible phenomenon.
Indeed, he was already being consumed, warped by the very mystery he had created.
Yosuke.
Yuhi stepped forward as if to shield me.
The wind blew.
I heard a sharp sound, and white cotton burst from the edge of the bed.
On closer inspection, there were marks on the bed as if it had been slashed with a blade.
A true paranormal phenomenon—yet the impossible shouldn’t be happening.
Huh? Ah . . . N-not this again . . . Th-this is . . . something else . . . It’s not me . . .
The man was making excuses with a pale face. I nodded in response.
Right. What just happened has nothing to do with you. It’s quite the coincidence that something like a Sickle Weasel phenomenon occurred here.
Coincidence?
The man was dumbfounded, but I continued talking to him without flinching.
You're no Sickle Weasel—just a criminal repeating malicious pranks. The weapon is . . . this, right?
I pulled out a nylon thread I had found at the scene with gloved hands and dangled it before him.
Ah . . . !
The man gasped, but I continued speaking.
A fishing line. You wrapped it around bicycles left on both sides of the alley, creating a simple trap. But . . . such a setup would be exposed as soon as the first person got caught, turning it into a police matter.
Holding both ends of the thread, I stretched it out to demonstrate.
Cunning, or perhaps cowardly—your more malicious act was to engineer the thread to break under slight stress. Look closely. Only part of the thread's fibers are stretched, which shows that it was pre-cut.
I thrust the thread in front of his eyes.
This way, even if someone got caught, the thread would snap before digging in too deeply. If the person wasn't barefoot or in thin clothes, it wouldn’t even cause injury. That's why most victims were women. Or rather, were you specifically targeting women in skirts?
. . .
The man listened to me with a stern face.
Well, that’s why the pranks didn’t surface as incidents, and only the rumors of whirlwind blades spread like an urban legend.
Just then, Yuhi tugged at my clothes.
But Yosuke, if the cut thread was left behind, wouldn’t it be obvious it was a prank? It became a rumor because people got hurt in a place with nothing around, right?
I replied to my sister's sensible question.
The incidents mostly happened in the evening. On that dark path, you wouldn't easily find a severed thread. Additionally, the setup could be retrieved during work hours. He was scheduled for a shift the day after each incident.
I then glanced at the thread in my hand.
However, since the bikes were illegally parked, I suspected there might be instances where you wouldn't get to collect the thread. The bike's owner could ride off before the thread was retrieved, especially if they regularly used that spot. And that's exactly how we found this evidence.
But then the man retorted with a half-smile.
Evidence? Sure, this might prove some setup was done, but . . . it has nothing to do with me.
True, this is evidence that the incident was man-made, not proof that you are the culprit. Depending on the situation, my duty would have ended here, but given your state, it doesn't seem to be the end yet.
I looked at him with pity.
Still, the wind blew inside the room, its source the man in front of me.
But in my opinion, there is evidence that you are the culprit—likely right here in this apartment.
I glanced around the cramped room.
There seems to be a purpose behind your actions. You didn’t just set up the trap for the sake of it. Maybe you filmed the moment the victims fell into the trap with a hidden camera, or perhaps brought back some sort of trophies.
I spoke while intently observing the man's expression.
The man's eyes darted around, and his gaze shifted toward the desk.
Yuhi, over there.
As I pointed, Yuhi walked up to the desk and reached for the top drawer without hesitation.
I suspected as much because of the smell of blood.
S-stop!
The man shouted.
A sound, similar to the bed tearing earlier, echoed through the room.
But this time, a slightly stronger breeze blew within the closed space, causing the window curtains to flutter.
That was the only change.
That was close. If it hadn't been for me, you might have been injured, you know?
Huh?
As Yuhi turned around and smiled, the man gasped as if he had seen something terribly frightening.
After glancing at the trembling man, Yuhi opened the drawer.
Yosuke, there are lots of these in the drawer.
What she pulled out was a small glass bottle.
Inside were things resembling rolled-up threads.
These are threads recovered from the scene, all slightly stained with blood. If we match them with the victim's DNA, we can conclusively determine they were used in the crime. If acquiring these results was the goal, then the trap was just a means to an end.
I observed the inside of the small bottle and sighed.
Finally, the man seemed to resign himself and lowered his face.
Were you interested in the blood of women? Or was harming women your goal?
At Yuhi's question, the man's shoulders jerked.
W-well . . . no . . . I-I . . .
He lifted his head, overwhelmed by some uncontrollable emotion.
I don't desire the blood itself . . . It's the thin, sharp objects on a woman's skin. Cutting into the flesh, severing blood vessels . . . those scars irresistibly attract me. I know, it's abnormal. It's because of its abnormality that I . . .
The wind suddenly blew stronger.
It was like it had responded to his intensified emotions.
But I never imagined it would come to this! Am I not a human? Am I really some monster, a Sickle Weasel?
A gust of wind caused the papers in the room to flutter.
The curtains fluttered violently, and the sharp sound of the wind etched marks on various parts of the wall.
No, you are human. I'm about to prove that.
I pulled out a notebook from my pocket.
The cover was newly made of leather, but the pages inside were aged and faded.
Passed down from the previous generation along with my duty, this was my work tool.
It was the essence of my existence and an irremovable shackle.
Yuhi, can you restrain him for a while?
She nodded with a smile.
Of course! Finally, it's my turn to do something!
Yuhi stepped toward the man amidst the blowing wind, without hesitation.
A sudden, whip-crack sound erupted.
Instantly, a laceration was etched onto Yuhi's arm.
It was a phenomenon that would make anyone think of a Sickle Weasel spirit.
Ahh . . . that wound . . .
The man watched the scene, his expression one of dazed astonishment.
But soon, suspicion clouded his face.
Instead of fresh blood, a black liquid oozed from Yuhi's wound.
In the raging wind, it defied gravity, rising and writhing like a living thing.
What you saw just now was me cutting my skin. It saves the trouble of you doing it yourself.
Contrasting with Yuhi's beaming smile, the black liquid spread out like a net.
You . . . What on earth . . . ?!
Me? I am . . . a monster too far gone to be saved, perhaps? But you still have time—just leave it to my big brother.
Yuhi flicked her finger slightly.
Then, the black net enveloped the man swiftly and entirely, constricting him.
Ugh!
The man, bound by the black net, became immobilized.
The restraint seemed to affect more than just the physical, as the winds emanating from the man also ceased.
Now then, it's time to hunt the monster.
I stepped in front of the man, replacing Yuhi, and touched a page of the opened notebook.
I ask, does the Sickle Weasel exist or not?
The blank page glowed a pale blue.
Simultaneously, sparkling blue particles appeared around the man's body.
The light that emanated from the paper reflected in my eyes—it was the culprit transforming this man into a monster.
It comprised the thoughts of people who learned about mysterious incidents and believed in fantasies.
Normally harmless and powerless, but under certain conditions, it could become a deadly poison—poison that invades people.
Sometimes, mysteries transform people into monsters.
Therefore, someone must solve it.
I deny. The criminal acts in this incident were within human capabilities.
Aaaaah?!
As the man screamed, particles burst from his body and were absorbed into the notebook.
The light transferred the mystery and poison into an appropriate vessel.
I deny it. The suspect was identified during the investigation. His name is Teppei Ueki.
Uh . . . ah . . .
The man's voice turned hollow.
The particles lingering in the air gathered into the notebook, and the light intensified.
I deny. I secured the physical evidence that he is the culprit.
When all the particles have absorbed, I lifted my finger from the page of the notebook.
The fantasy had now been unraveled.
Given the above reasons, I deny the existence of the Sickle Weasel monster.
Having declared so, I snapped the notebook shut.
Instantly, the light vanished, and darkness filled the room again.
Ah . . .
The man's eyes rolled back as his body relaxed.
Yosuke, well done! I'm somehow more tired this time. The room smells awful.
Yuhi said, releasing the man from his restraints.
The black net that had enveloped him was absorbed into her wound, and the scar also disappeared.
Right. Are your wounds okay?
While carefully stowing away the notebook, I examined my sister's arm.
Eh? They're fine, aren't they . . . ? They've already healed.
Yuhi tilted her head in puzzlement.
No, I wasn't asking if they've healed . . . I meant they must have hurt, right?
Yuhi stared at my face for a moment, then silently hugged my arm.
. . . Yuhi?
I like that about you, Yosuke.
Yuhi spoke, pressing her forehead against my shoulder.
It's just a normal concern, though . . .
I was perplexed by her making such a big deal out of it.
Pain doesn't matter to me, not if it's for you, Yosuke.
. . .
Perhaps those were words I should have been happy about.
Yet, they sent a sharp pain through my heart.
Let's leave the rest to the police and head back quickly.
To mask the pain, I gently stroked her head.
Hmm.
Yuhi nodded, clinging to my arm.
We left the man lying on his back and departed from the littered room.
And so, the impossible phenomenon dissipated.
I exposed fantasies, leaving only reality behind.
I silenced rumors and solved mysteries.
It was almost like a detective's work.
This was my daily life. The life of Yosuke Mazekawa, the fourth son of the Mazekawa family.
