The Strongest Demon King Can't Conquer the World Because His Subordinates Are Total Disasters
Diabolos, the world's strongest demon king, should be able to conquer all continents in a single night with his overwhelming power. But his subordinates' imagination-defying incompetence keeps sabotaging every world conquest plan.
In Episode 1, the demon king's castle gathers an assortment of executives who are supposedly quite competent—yet everything they touch goes sideways. The military commander forgets battle plans immediately. The strategist loses critical documents. The Hell Duke bullie
The Strongest Demon King Can't Conquer the World Because His Subordinates Are Total Disasters - Between the manual and reality
Morning had come to the Chamber of Judgment.
Diabolos spread the map across his desk, arms folded, gazing up at the ceiling. The stonework Yuki had repaired days ago remained flawless as ever, the lava lamps casting smooth light across the walls. He'd spent last night reviewing defense plans again. Cutting supply lines through Permalis Port, fortifying positions around Gromd Caldera—the logic was sound. But there were no people to move. That wall still stood.
(Gareth Varoon. He should arrive today.)
Diabolos had read through the résumé Yuki had presented at the last meeting multiple times. Top graduate of Orbless Military Academy, the prestigious Ceriola institution. A hypothetical invasion plan his instructors said should be made into a textbook. Twenty years old. That number's weight seeped into two hundred forty years of exhausted memory.
He'd been expecting him. Honestly, quite a bit.
Footsteps sounded outside the door. Regular. Measured.
---
The report from the castle gate guards had come slightly earlier.
"Report, sir. The new strategist has arrived at the castle gate, but..."
The guard's tone was strange.
"Then let him in."
When Diabolos spoke, the guard paused.
"That's the thing—he won't come in, sir."
"...What?"
Yuki supplemented from the wall, expressionless.
"[serious] According to the gate captain's report, he's standing at attention in front of the gate. Watching a pocket watch."
"..."
Silence.
"What time is it now?"
"Eight fifty-nine in the morning, sir."
"..."
More silence.
Only the sound of lava sliding down the chamber walls. Dolkias Melve was writing something on documents in the corner, and he looked up. A thin man with thin fingers, eyes constantly busy. Always like this. Even today he'd brought documents before the meeting.
"Quite the meticulous fellow!"
"Shut it."
---
9:00:00 AM.
The chamber door opened.
The man who entered had a perfectly straight spine. Silver-white short hair flowed neatly to the side, strong blue eyes fixed in a straight line on Diabolos. His military uniform was starched crisp, not a single wrinkle. Under his arm—a thick book. Gold lettering on the cover read "Standard Conquest Operations Manual, Seventh Edition."
The man took three steps from the door and stopped. Heels together, arms at his sides. Upper body tilted forward thirty degrees, held for two seconds. Back to vertical. Again thirty degrees. He repeated this three times.
A perfect three-stage salute.
The angles were impossibly precise.
Dolkias let out a small "Oh..." Yuki narrowed her eyes, comparing the résumé to the man before her. Diabolos—started to lean forward, caught himself, and deliberately settled back into his chair.
"[serious] Gareth Varoon. As of today, I assume the position of Strategus—Genius Tactician. I look forward to working with you."
Stiff, if you wanted to call it that. But each word carried density.
Diabolos rose from his chair.
"[serious] I'm Diabolos. The Demon King. Now then—"
"Please allow me to distribute the invasion plan. I've prepared it in advance."
Gareth quickly extracted papers from the manual. One copy for each person.
Diabolos glanced at the sheet he received.
The ink was clean. No sources missing. No stains. The letters weren't mirror-written. Readable. All of it.
(This should be normal...)
Noticing he was almost moved by this, Diabolos bit down on his back teeth.
---
The moment Yuki read the first page, her eyebrows moved.
Barely. The change in expression was near the minimum unit possible. But Diabolos didn't miss it.
Yuki placed a finger on one line.
"[serious] I have a question. The plan's first objective—the capture of Permalis Port."
"It's based on the priority order in Manual Chapter Three, Section Seven. The procedure involves starting with the blockade of a trade port, then systematically cutting supply lines."
"[serious] That port was fortified by the Holy Pilgrimage three years ago. The inner walls contain an alloy mixed with holy-blessed silver. The structure is designed so that demons weaken their connection to the source vein just by approaching."
"That's not in the Seventh Edition of the Manual."
"[serious] Whether it's in the manual or not, it exists in reality."
"Information not in the manual is treated as unconfirmed. Manual Chapter Two, Section Four—"
"[cold] So you're saying a fortress that actually exists should be treated as unconfirmed?"
Her voice was subzero. Dolkias shrank a little in his seat.
Gareth's expression didn't change.
"If you wish to confirm it, please submit a formal information update application. After review, it will be reflected in the manual."
"[serious] How many days will the review take?"
"At the earliest, thirty days."
"[cold] The Holy Pilgrimage will move this week."
"That's also unconfirmed information."
A wrinkle appeared between Diabolos's eyebrows.
"[serious] Both of you—"
"Your Majesty, please follow the mediation procedures in Manual Chapter Eight, Section Three. First, designate a neutral third party, then both sides present the key points of their arguments in writing—"
"[angry] Do I need to find a third party? In my own castle?"
"It's not a matter of procedure, but rather the intent of Chapter Eight—"
"[serious] I also have opinions about Chapter Eight. Particularly Section Five of Chapter Eight—"
The argument split in two directions.
Gareth answered Yuki, Yuki countered Gareth, Gareth supplemented Diabolos, Yuki objected to Gareth. The lava continued flowing quietly through the Chamber of Judgment. Dolkias followed the three-way conversation while writing something on documents, his eyes darting back and forth.
Something accumulated inside Diabolos.
Two hundred forty years of accumulated patience, about to be spent all at once right here.
"[angry] Everyone shut up!!"
Infernal flames shot toward the ceiling. Black-purple fire dyed the Chamber of Judgment for a single moment, making the lava on the walls shudder.
Gareth reflexively opened his mouth.
"[serious] Threatening behavior is covered in Manual Chapter Twelve—"
"[gentle] Ah, that manual."
Dolkias looked up from his documents. His voice was leisurely.
"I spilled coffee on it yesterday. Chapter Twelve is now unreadable."
Silence fell.
Perfect. Complete silence.
Gareth opened his mouth, then closed it. Opened it again, closed it again. His blue eyes swam through empty space.
"...Without Chapter Twelve being readable, I cannot verify the procedures for this discussion. It cannot continue."
Yuki spoke quietly.
"[sarcastic] So by that logic, Your Majesty's infernal flames are currently permitted under the rules?"
Diabolos realized his actions had just been defended by Yuki.
It was complicated. Very.
---
Silence continued in the Chamber of Judgment.
Gareth placed the plan precisely on the desk, standing with perfect posture. Yuki returned the documents to her lap, eyes lowered. Dolkias began quietly hiding the coffee-stained manual under the desk.
Then.
The pulse-resonance stone set into the wall—a crystallized mineral of source vein energy used for long-distance communication—vibrated violently.
Everyone looked up.
"[serious] Report. Holy Pilgrimage reconnaissance unit, estimated two hundred personnel, confirmed landing at Morg Zalen's south shore."
Diabolos stood.
"What's the interception strategy?"
Without hesitation, Gareth raised his hand.
"I have one."
He extracted another sheet from the manual. Deployed it on the map in thirty seconds.
"[serious] Against a reconnaissance unit of two hundred, deploy an interception force of four hundred to the south shore. Seal the sea route and eliminate them completely. Standard anti-reconnaissance procedure based on Manual Chapter Five, Section Two."
Fast. Diabolos looked at the map. The logic held. The numbers were accurate.
(Fast...)
He was genuinely impressed.
Yuki opened her mouth.
"[serious] One point of confirmation."
Gareth turned his gaze toward her.
"This plan assumes the reconnaissance unit is purely reconnaissance-focused. Have you considered the possibility of a feint?"
"That level of caution against a reconnaissance unit is excessive. Manual Chapter Five, Section Two—unexpected operations invite complexity and increase failure risk."
"[serious] Orvan Drexia, the Holy Pilgrimage's leader, is a former mercenary captain. He doesn't move by the textbook."
"That's also—"
"Unconfirmed information, I presume?"
Her voice was quiet. Toneless.
Gareth closed his mouth for just a moment.
Diabolos was looking at the map. The south shore position. The interception force's deployment route. The orderly lines of the plan. And Gareth's speed—that relentless speed and confidence. In three days of subordinates bringing nothing but source documents, mirror-writing, and punishment, this was the first genuinely competent pace to emerge.
Yuki's warning made sense. It was logical.
But.
"Approved. Deploy four hundred to the south shore."
Yuki opened her mouth for just a moment.
Closed it.
"...Understood."
Her tone didn't change. Her expression didn't change. Only her gaze fell to the documents before her, and something hardened in silence. Diabolos wasn't watching that expression. He was making notes on the map.
---
Thirty minutes after the interception force departed for the south shore.
Quiet had returned to the Chamber of Judgment. Gareth was organizing his plans. Dolkias had spread out new documents. Yuki had stopped writing and was simply looking out the window. The sky over Morg Zalen was always a heavy gray.
The pulse-resonance stone vibrated.
Everyone looked up.
"[serious] Report. Holy Pilgrimage unit, estimated six hundred personnel, has infiltrated the eastern source vein concentration zone. No contact with interception force."
Diabolos stood.
"The east?"
A second vibration.
"[serious] Three simultaneous sabotage operations confirmed on the eastern source vein supply lines."
Source vein supply lines—the fundamental pathways drawing the source vein, the wellspring of magical power flowing through the earth, into the castle. The defensive barrier of Volnagrad was maintained by the magical power supplied from there.
Three locations. Simultaneously.
A third vibration.
"[scared] The Demon King's castle defensive barrier has dropped to forty-seven percent of normal capacity."
Silence fell over the Chamber of Judgment.
Only the sound of lava flowing down the walls continued.
Diabolos looked at the map. South shore. And east. The overlapping lines took on clear meaning. The reconnaissance unit was a feint. The main force had been targeting the east from the start. While eyes were turned to the south shore, they drove straight into the source vein concentration zone.
Orvan Drexia. Former mercenary captain. A man who doesn't move by the textbook.
—That's why Yuki had said it.
"What's the defense situation in the east?"
His voice was low. The words were directed at Gareth.
Gareth began flipping through the plan pages. Chapter Five. Chapter Six. His finger ran across the paper.
"This pattern is...not in Chapter Five...Chapter Six, Section Three is close, but the manual..."
His face was going white. His finger stopped. Couldn't stop. Moved again. Stopped again.
"...isn't..."
The pages wouldn't turn anymore.
Yuki spoke quietly.
"That's why I told you."
Her voice was anger held back. But held back, it sank heavy into the room.
Gareth looked up. He looked at Yuki. Yuki wasn't looking at Gareth. She was looking at the defensive barrier capacity report, expressionless. Forty-seven percent. Yuki's gaze rested quietly on that number.
Dolkias was curled up small, still holding his documents.
Diabolos placed his fist on the desk.
He didn't strike it.
He placed it. Just that action. That alone made sound in the silence.
"...This was my judgment error."
No one said anything.
"I approved Gareth's plan.