There were two chairs.
Seung-woo occupied one of them, drinking canned coffee.
"What about the customers?"
"Three came and left. I handled them through consultations."
"And the inspections?"
"You haven't used any today."
"Then take a look at mine."
"I've already inspected your skill."
"That was only once, and I've entered Gates four times since then. Check whether anything's changed."
His reasoning sounded plausible.
But I knew he'd actually been sitting here since morning, counting how many people came and went.
He simply didn't like the thought of me sitting alone on a day without customers.
"Have a seat."
[Structure Inspection].
The colors drained away.
A network of lines appeared above Seung-woo's right hand.
It looked exactly as it had three days ago.
The switch was firmly settled in the position where I'd moved it, and Mana was still leaking from the same three points.
There were no problems.
So I went deeper.
Three seconds.
I passed the plate of the Conversion Unit.
Below it was something indistinct. A place that had a definite position but no discernible shape.
The Signature.
Something stamped identically at the very bottom of every skill in this world.
It was both a seal certifying that the skill originated from the System and a prerequisite for the skill to function.
A document without an official seal wasn't a document.
It was just paper.
If the Signature disappeared, all that remained of the skill would be an empty shell.
Four seconds.
I maintained my focus.
Pressure began building at the back of my head.
Five seconds.
It flickered.
Just once.
The Signature went dark for a fraction of a second before returning.
It was exactly what I'd seen when I inspected Yoo Ji-su a few days ago.
At the time, I'd assumed it was because I'd pushed myself too hard.
I opened my eyes.
"Did you find something?"
Seung-woo asked.
"Mr. Seung-woo."
"Yes?"
"Could you activate your skill once? Don't fire it at anything. Just gather the flames in your hand."
Seung-woo raised his hand.
A red glow gathered near the inside of his wrist.
I opened the structure again.
This time, I didn't examine the upper layers.
I went straight to the bottom.
I wanted to see what happened to the lowest layer at the exact moment the skill activated.
The Signature brightened.
When Mana passed through it, the Signature flashed once, and that flash acted as a signal that opened the circuits in the layers above.
Then, as the flash ended, it briefly faded.
I observed it twice.
The same thing happened both times.
I opened my eyes.
Four seconds in total.
"Mr. Seung-woo, one more time."
"Again?"
"This is the last one."
The third attempt was the same.
Pressure built at the back of my head rather than my temples.
For a moment, I couldn't get up from my chair.
Seung-woo held out a water bottle.
"Are you all right?"
"I'm fine."
I accepted it and drank half.
Over seven years, I'd opened hundreds of skills.
I'd descended all the way to the Signature Layer in roughly half of them.
Those were the cases where Han Do-gyeong had written 'Deep Inspection' on the request forms.
Back then, I'd seen the Signature every single time.
It was always the same seal.
No matter which skill I opened, it looked identical.
Because of that, I'd treated it as part of the background, like the pattern on wallpaper.
Something that didn't need to be examined.
I'd never once thought to measure it.
Its brightness.
Its thickness.
How long it remained illuminated.
Because I'd never considered the possibility that those values could change.
I opened my notebook.
On the fourth page, I drew a table.
Date. Subject. Skill. Signature Response.
I entered Yoo Ji-su's case from three days ago in the first row.
Then I recorded Seung-woo's three observations from today.
There was hardly anything to write.
The Signature flashed, then faded as the flash ended.
That was all.
I needed numbers.
How many seconds did it remain illuminated?
How much did its brightness decrease?
To measure those values, I'd have to examine several skills under identical conditions.
And if I could only perform two inspections a day, gathering enough observations would take months.
I put down my pen.
I'd have to approach this differently.
I had seven years' worth of blueprints stored in my memory.
The Signatures weren't included in those blueprints.
I'd never drawn a Signature because the request forms had never required me to.
But I remembered seeing them.
I closed my eyes and retraced my memories.
The skills I'd inspected during my first year.
[Flame Projection].
Sixteen inspections.
The first time I'd opened that skill was in the spring when I was twenty-two.
What had the Signature looked like back then?
It had been distinct.
It had a recognizable shape.
Now it had no discernible shape.
I'd been blaming that difference on my own perception.
My twenty-one-year-old body could only inspect structures at a relatively shallow depth.
At twenty-eight, I could descend to the very bottom in 0.3 seconds.
Naturally, everything looked blurred to me now.
That was what I'd assumed.
But there was something wrong with that reasoning.
My twenty-two-year-old self hadn't been particularly capable either.
I'd only been awakened for a year.
There was no reason I should have been better at inspecting structures then than I was now.
Yet something I'd been able to see clearly back then appeared indistinct at the same depth today.
My eyesight hadn't deteriorated.
The thing I was looking at had become blurred.
A chill ran through my head.
Then a question I'd set aside three days ago resurfaced.
Skills with the same name were supposed to have the same blueprints.
Because the System produced them.
Yet Park Seung-woo's [Flame Projection] had an Activation Unit attached in the wrong position.
And that D-rank Hunter's [Delay] had two switches.
I'd recorded those anomalies as Individual Variations.
For seven years, nobody had questioned that explanation.
If products coming out of a factory all had different wiring, perhaps the problem wasn't with the products.
Perhaps it was the factory.
Seung-woo was waving his hand in front of me.
"Mr. Yoon Jae-ha. Mr. Yoon Jae-ha."
"……Yes?"
"You've been sitting like that for three minutes."
"I'm sorry."
"Did you find something wrong?"
Something wrong.
I didn't know how to answer.
Seung-woo's skill was functioning normally.
If he entered a Gate today, his flames would fire in 0.4 seconds.
There was nothing wrong with that.
The problem was that the seal stamped at the bottom of his skill was fading.
And that wasn't a problem with Seung-woo.
It was a problem with whoever had stamped the seal.
I knew absolutely nothing about whoever had done that.
I didn't even know their name.
"No."
I answered.
"Your skill is perfectly fine, Mr. Seung-woo."
It wasn't a lie.
＊
Jeong Tae-sik arrived that evening.
He wasn't wearing his helmet.
That seemed to be his own way of signaling something.
"Mr. Yoon Jae-ha. It's about my shield."
"Is something bothering you?"
"No, it's working well. So well that I came to see you."
Jeong Tae-sik raised his shield.
"Remember how you concentrated the Mana toward the top? I've entered Gates twice since then, and the upper section is incredibly tough now. Kobold pickaxes bounce right off it."
"I'm glad to hear that."
"But something strange started happening yesterday."
My throat suddenly felt dry.
"What happened?"
"It's just as tough as before, but it's taking longer to activate. My Mana Barrier used to appear the moment I raised my shield. Lately, there's a slight delay."
"How much of a delay?"
"I'm not sure. Half a beat, perhaps? But I got hit once because of that half-beat delay."
Jeong Tae-sik touched his left shoulder.
I'd already used both of today's inspections.
In fact, since I'd divided them up while having Seung-woo activate his skill three times, I'd effectively exceeded my limit.
The pressure at the back of my head hadn't gone away, and afterimages had begun lingering in my left eye.
Even so, I inspected it.
[Structure Inspection].
Three layers appeared over Jeong Tae-sik's shield.
The middle layer was concentrated toward the top, exactly where I'd moved it.
The lower section was thinner.
Everything was as expected.
The problem was at the very bottom.
Three seconds.
The Signature was blurred.
More blurred than Seung-woo's.
It took longer to begin glowing, and that delay meant the circuits above it opened later.
Half a beat.
Exactly as he'd described.
I opened my eyes.
My vision doubled.
For a moment, I saw two of Jeong Tae-sik's faces before they merged into one.
"Mr. Yoon Jae-ha."
"……Just a moment."
I braced my hands against my knees and steadied my breathing.
I didn't vomit.
I hadn't eaten anything yesterday, so there was nothing to bring up.
"Mr. Jeong Tae-sik."
"Yes?"
"This isn't because of the changes I made."
"Then what's causing it?"
How was I supposed to explain?
That there was a seal at the very bottom of his skill, that the seal was necessary for the skill to activate, and that its fading brightness was causing the activation delay?
That I didn't even know who had stamped that seal?
"I'm still investigating."
I answered honestly.
"I think I understand the cause, but I don't know how to fix it. Please give me some time."
Jeong Tae-sik nodded.
"Then I'll just raise my shield half a beat earlier until you figure it out."
"……What?"
"If the barrier takes longer to appear, I just have to raise my shield that much sooner, don't I?"
I stared at him.
"Spend ten years as a D-rank Hunter, and you learn to handle at least that much."
Jeong Tae-sik strapped the shield onto his back.
"You take care of fixing it, Mr. Yoon Jae-ha. We'll take care of holding out until then."
＊
That night, I wrote four lines in my notebook.
The Signatures are fading.
The rate differs between individuals.
As a Signature fades, skill activation becomes slower.
Severity: Jeong Tae-sik > Park Seung-woo > Yoo Ji-su.
Beneath the last line, I drew three question marks.
Why was Jeong Tae-sik the worst affected?
Of the three, he'd been a Hunter the longest.
Ten years.
Seung-woo had been one for three years, and Yoo Ji-su for four.
Did frequent use cause the Signature to fade?
If so, what about A-rank Hunters?
Cha Yu-gyeong had said she used her right arm twenty-four times a day.
Even on days when she didn't enter Gates.
＊
My phone rang.
It was an unfamiliar number.
I answered.
"Am I speaking with Mr. Yoon Jae-ha?"
It was a young man's voice.
Professional and polite, with the practiced tone of a call center employee.
"Who's calling?"
"I'm calling from the General Affairs Team at the Skill Research Institute, an affiliated institution of the Hunter Association."
I looked at the ballpoint pen resting on my notebook.
It wasn't rolling.
The desk was perfectly level.
"We're contacting you regarding a potential research collaboration. Would you happen to have any availability this week?"
"……What kind of research?"
"The person in charge will explain the details to you directly. Our Director has taken a special interest in this matter."
Seven years ago, this call had never happened.
Because I'd met him directly in the corridor of the assessment center.
This time, I'd refused him on the spot.
And because of that, the sequence of events had changed.
"How did you get my phone number?"
There was a brief silence.
"It's in the Association's registration records."
That was a lie.
Association registration records fell under the jurisdiction of the Administration Headquarters.
Affiliated institutions had no authority to access them.
I'd confirmed that missing connection when I drew the organizational chart yesterday.
Which meant someone had crossed a boundary they weren't supposed to cross.
"I'll think about it and get back to you."
I ended the call.
Then I closed my notebook.
It had taken Han Do-gyeong nine days to find me.