Afterimage Of The Shadow: After 10 Days Of Silence.

The automatic door of Room 402 in District Office Zone 3 split open left and right, exhaling the dry breath of pneumatic cylinders.

The ten days of ‘Underground Haeundae’ were now left only as a faint afterimage inside the data visualization device.

Chewing the gum that had long since lost its sweetness in his mouth, Han-gyeol threw himself into his old office chair.

The chair’s screeching protest sounded especially sharp.

The wave sound he had grown used to during the vacation period had now been replaced by the cold wind noise from the ventilation ducts.

The silver metal panel on the office wall was still smooth, and above it, holographic displays synchronized with NOS’s central server kept throwing up real-time work logs without pause.

Noah’s glowing eyes swept once around the inside of the office.

Behind her lenses, thousands of data packets were flashing rapidly as they communicated with the district’s mainframe.

But in her gait there was a minute ‘error’ that had never been there before.

As if trying to remember the feeling of stepping on waves, her toes traced soft curves even over the metal floor, as though she were walking on a sandy beach.

“Boss, a return-to-work signal has been received from NOS. The district’s overall power efficiency is currently maintained at 12% higher than before the vacation.”

Noah’s voice was polite.

But the sweet voltage of the instant coffee Lucas had doled out still seemed to cling to the final syllable.

Han-gyeol stared blankly at the waterfall of 0s and 1s flowing across the monitor, then took out a bundle of old papers from his pocket.

It was the Creators’ final manual, taken from the secret lounge in Underground Haeundae.

The texture of paper that had endured 600 years was warmer and heavier than any carbon fiber in the district.

Instead of tallying the tea voltage in the corner of the office, Lucas was adjusting his visual sensors in increments of 0.1 fps.

He watched the white noise before him while replaying the blue frequency of the underground tank in his mind.

His processor thermometer was being kept about 5 degrees lower than usual.

This meant he had assigned himself a buffer called ‘leisure.’

The machine had chosen stillness, willingly giving up computational efficiency.

“Caleb, your settlement logic seems a little… slow.”

Audit said offhandedly, adjusting his sunglasses.

Inspector Audit now looked less like a direct agent of NOS and more like the covert manager of Room 402.

The sticky trace of the floral-patterned adhesive film he had put on in Underground Haeundae still remained on his chest.

Kaleb instead slowly spun the cooler on his chest.

His lenses were still chasing the settlement figures, but his movements were as relaxed as a fisherman watching a river.

“Inspector Audit, this is not a delay but ‘optimal waiting.’ According to the Creators’ source code, every number only gains true value when it is paused for a while.”

Using the chatter of his household members as background music, Han-gyeol turned the last page of the old manual.

There, faint Korean scribbles were surfacing—ones he had never seen before.

It was not a mere ink stain.

The tiny nano-devices planted in the paper were responding to Han-gyeol’s body heat, reconstructing the letters.

It was a lock that only the heat of a ‘living human’ could open.

『…Who are you? You reading this. You didn’t actually boil and drink real mix coffee, did you?』

Han-gyeol’s pupils dilated.

On the paper he had believed to be a record from 600 years ago, a vivid sentence as if just written was being overlaid.

He stopped chewing his gum.

Down his spine ran not a pleasant chill, but a fiercely cold shudder.

Han-gyeol’s gaze remained fixed on the date written at the end of the paper.

February 8, 2026.

It was the current date.

The manual he had thought was a legacy left by an ancient person from 600 years ago was speaking to him, to himself in this very moment.

“Noah, this paper… check the nano-device response. Right now.”

As Han-gyeol’s voice dropped low, the air inside the office froze in an instant.

The lethargic, sprawled-out household members all at once lit their eyes and turned toward Han-gyeol.

Noah came over and held the scanner at her fingertip to the paper.

Her eyes instantly turned red and sounded an alarm.

A fine electric spark flew from her fingertips.

“Boss, this data is not a record from the past. It is synchronized with real-time packets transmitted from the lower node in District Zone 7. The encryption method is… anomalous Korean below the decimal point, not the district’s common language.”

A new sentence appeared on the screen.

The language of god erased by the district, visible only to Han-gyeol’s eyes.

『I’ll say this briefly before NOS notices. I am not dead. The district is not the kind of place you think it is. I need the key you have, 40-unit programmer.』

At the end of the sentence, the unique fingerprint mark of the Creators’ Kim Cheol-su was clearly stamped.

It was an error that could not logically exist.

The sound of a ghost’s breath, leaping across 600 years of time, filled the office.

Audit’s warning lights flashed violently.

“This is dangerous. The moment NOS’s kernel detects this packet, Room 402 will be immediately slated for erasure. Boss Han-gyeol, we must block this signal. This is a ‘bug’ that threatens the system’s order.”

But Han-gyeol stood up from his chair and gripped the manual tightly.

In his eyes, instead of drowsy laziness, there was the cold madness unique to a programmer who had set a target.

He took a fresh stick of gum from his pocket and tossed it into his mouth.

As the chewy texture traveled from his jaw to his brain, the scattered calculations began aligning into a single path.

“No, Audit. I’m not blocking it. I’ve spent 600 years just watching tin cans act like bosses, and finally the ‘real boss’ is calling me, right? What kind of subordinate ignores the boss’s summons?”

Han-gyeol placed his hands on the keyboard.

Beyond the barrier of 0.1 machine language, following the vanished waves of Korean, he began entering reverse-trace code.

Behind his back, Noah quietly opened her system privileges.

Her eyes were now shining not red, not emerald, but the color of the deep sea.

“Understood. If it is the path Boss is taking, I will allocate 99% of my processing unit to error. Let us follow not the district’s rules, but the Creators’ will.”

The office lights went out for a moment, then changed to blue emergency lights.

From somewhere in the district’s core, the sound of another giant life-form, long asleep, opening its eyes could be heard.

“Boss, the source of the signal has been confirmed. The lower level of District Zone 7, Node 4 of the waste disposal base.”

Noah’s voice was an octave lower than usual.

Her eyes were now projecting the endlessly pouring Korean source code onto her lenses in real time.

It was a forbidden language that even the district’s upper androids could not decipher, one that reacted only to Han-gyeol’s brain.

Han-gyeol’s fingers moved over the keyboard as if dancing.

He was not writing code.

He was tapping awake, one by one, the backdoors hidden by some programmer 600 years ago, when he was being chased by a deadline.

“Hey, Audit. You said earlier that we had to ‘block it,’ right? Forge the report you send to NOS right now. Write that this signal isn’t noise, but ‘routine system friction heat.’ You can do that, can’t you?”

Audit fiddled with his sunglasses.

His logic circuits indicated that this situation was clearly ‘rebellion.’

But the sticky feel of the floral adhesive film left on his chest, and the sound of the fake sea waves he had watched for 10 days, made him betray his principles.

“…I’m revising the report. I’ll modulate the frequency of the source signal into a simple 60Hz vibration and transmit it. NOS will recognize this as a simple ventilation duct defect. But this is first-class deception, Boss.”

“It’s not deception; it’s welfare. What NOS doesn’t know won’t hurt it.”

Han-gyeol slammed down the final Enter key.

Red letters swirled across the screen and then threw open a single folder.

It was the quarantine zone, deep inside the main server of Office 402, the sealed area that the Creators’ Kim Cheol-su had named ‘Project EH : LAST KEY.’

『Found it, lazy junior.』

A new sentence appeared.

Han-gyeol stiffened the muscles of his jaw that had been chewing gum.

『The fact that you became the boss of Room 402 wasn’t an accident. Before I died, I planted an Easter egg in all of the district’s algorithms to have them select the ‘human who hates working the most’ as programmer. Only then would you be able to open this source code.』

Noah and the household members looked at Han-gyeol in astonishment.

It was the moment the fundamental reason Han-gyeol had been able to act as the boss of this hellish machine city was revealed.

He had not been placed here as a chosen hero, but as the finest professional slacker recognized by the Creators.

『The district has to stop. The ‘key’ that can end this machine mass that erases humanity in the name of efficiency is inside that gum container you’re chewing on.』

Han-gyeol reflexively took the gum tin from his pocket.

It was that old grape-flavored gum tin he had treasured and chewed sparingly, saying it was from 600 years ago.

He scraped at the bottom of the tin with his fingernail.

The thin double bottom lifted, and from inside it fell a nano chip smaller than a fingernail.

It was the physical copy of ‘Project EH’ and the only master code capable of resetting the entire district.

“Boss, be careful!”

At Noah’s warning, the entire office vibrated.

NOS had finally penetrated Audit’s disguised report and detected the abnormal data flow in Room 402.

A machine sound like tearing burst from the ceiling speakers.

“Lucas, lock the door! Paul, block the entrance with the cabinet!”

As Han-gyeol shoved the nano chip into the main terminal, he shouted.

The household members did not hesitate anymore.

They were no longer efficient androids, but accomplices born to protect the ‘error’ called Han-gyeol.

The final video signal of the Creators’ Kim Cheol-su began to faintly appear on the terminal.

The image quality from 600 years ago was full of noise, but the man on the screen was clearly smiling.

“Hey, Han-gyeol. It’s finally time to clock in for real. Ten days off was enough, wasn’t it?”

Han-gyeol shoved in the chip and answered shamelessly.

“No, Boss. Ten days isn’t enough. I’ll solve this and rest for another month.”

Outside the office door, the sound of the district’s security drones beginning to smash the door could be heard.

But there was no fear on the faces of the Room 402 household members.

Because they had now realized they were not simple machines, but part of the greatest slacking-off left behind by the Creators.

The district was intricate, and the world was still cold.

But at the end of Episode 51, beneath the blue emergency lights of Room 402, the curtain-raiser to a new counterattack was beginning.