After conquering the world with the cultural phenomenon known as "Love and Theory," Atem and Kaiba find themselves invited across the globe by royalty, governments, and research institutions eager to meet the King of the Afterlife and his partner.
What begins as diplomatic visits quickly becomes an international honeymoon.
From royal banquets and political summits to magazine interviews, bestselling travel features, and an unexpected invitation from the Duat itself, the newlyweds discover that every attempt at a private vacation only makes them more famous.
The world calls them symbols of love and reason.
The afterlife calls them quantum marriage.
Kaiba calls it a logistical nightmare.
Atem calls it destiny.
This is a translation of an original work on Pixiv.
Original Title: 愛と理論 12 王、新婚旅行へ行く
Original Author: 葉人(@Hathor₋yuki)
Personal site: https://prideshipping.sakura.ne.jp
But already the name had transcended culture and preference to become an international symbol.
Royal households, governments, and research institutions from country after country sent invitations.
For one reason only: "We want to see the King of the Afterlife — and his partner — with our own eyes."
The Kaiba mansion.
Seto sat with his arms folded before a tower of stacked invitations on the table.
"I've read through thirty-six of them. …Every single one wants you under the pretext of 'sweets diplomacy.'"
"Diplomacy is also a place for deepening mutual understanding. If we're invited, we should go."
Atem smiled his usual unhurried smile and picked up one of the letters.
"The problem is that my name appears alongside yours."
"Naturally. You're my partner. It's only right to go together, as the King's companion."
"…I can't shake the feeling of being dragged along."
Seto narrowed his eyes just slightly. Atem gave a quiet laugh.
"Then stand beside me as the King's theory. With your composure there, every country will receive us correctly."
"Heavy words from a king."
"And true ones."
The first destination: a kingdom in Northern Europe.
The banquet hall was decorated in patterns of snow crystals, the air crystalline and clear.
The doors opened, and Atem appeared — draped in golden light.
The atmosphere of the room trembled at his presence.
Seto followed a step behind in a deep navy suit — cold and precise, immaculate.
Less conspicuous than anyone, yet more magnetic than everyone.
His presence was like reason itself standing at the side of a king.
When Atem stepped forward, Seto matched him a half-step behind.
When someone approached, Seto received them and returned with exactness.
The whole shape of the diplomatic occasion shifted on the breath of two people alone.
The King, and his theory.
That was what people called them.
Night. The backstage room.
The banquet over, Atem turned his glass slowly between his fingers.
"Seto. Tonight's gathering… it felt something like faith."
"The boundary between faith and diplomacy is never very clear."
"Did they come to see me — or to see us?"
"The latter."
Seto answered immediately.
"The world is looking for proof that love and theory can coexist. You are the symbol. I am the evidence."
Atem smiled quietly and leaned toward Seto.
"Then in the next country too, let us prove it."
"…Fine."
Their glasses touched with a soft sound.
The diplomatic night had begun, quietly, to illuminate the next stage.
The destinations kept multiplying.
In Europe: "a symbol of the new monarchy." In Asia: "the ideal form of a couple." In America: "a model for the fusion of next-generation AI and ethics."
The world, right now, was captivated by the King of the Afterlife and the man of theory.
The palace in London.
Press and diplomats crowded in; figures pressed against every gap in the curtains for a glimpse.
Atem walking the red carpet was like a living golden myth.
With every step he took, even members of the royal family held their breath.
Seto walking beside him radiated the same presence — but not the same quality.
Not Atem's kind of light. Something more like structure.
A beauty quiet and unbreakable, like a perfectly constructed theorem.
"Seto. …Everyone's eyes are dazzled again."
"You're simply bright."
Seto's reply sounded composed — but his voice held something quietly proud.
"But today's agenda is politics. Are you planning to conclude international negotiations with a single royal smile?"
"There is nothing a king can do that you cannot."
"Logical basis?"
"Love."
That single word left Seto without a response.
Somewhere in the press seats, a camera shutter clicked, softly.
The next day's headline read:
"Reason and Love at the Forefront of Diplomacy" — Afterlife King Atem, accompanied by Kaiba Seto, the King of Theory, captivates world leaders
Political papers and economic journals alike had begun, at last, to place romance in their headlines.
The banquet in the Middle East that followed.
The kings assembled there received Atem as an equal — a fellow king — and showed Seto the deference owed to a sovereign of theory.
Atem raised his cup, weaving in a prayer from an ancient tongue.
"Civilization does not end. As long as love and theory exist together, everything blooms again."
Seto set down his cup beside him and continued, quietly:
"Love exists outside the structure, and theory within it. But when the two make contact, the system is complete."
Silence.
Then: a thunderclap of applause.
Speaking in different languages, Atem and Seto had spoken the same truth.
Night. The balcony of their lodgings.
Stars scattered across the desert sky above; in the distance, an oasis light trembled.
Atem looked up at the sky.
"Seto. The world needed this so much."
"Needed what?"
"Theory in love. Love in theory."
"…And humanity in a king."
Seto moved one step closer and looked up at the night sky over Atem's shoulder.
"If you are the flower, I am the pillar. Whatever storm comes, I won't break."
Atem turned, narrowed his eyes, and smiled.
"Then I'll keep blooming, trusting the pillar."
The moment their hands met, the stars burned brighter.
As if the world itself were recording the vow.
Their journey was not yet over.
"More diplomacy…?"
Atem finished reading through the materials and looked at the file on Seto's desk.
The gold-bound cover listed, page after page, scheduled banquets and courtesy visits with royal families and heads of state from around the world.
"It's the sweets effect." Seto answered. "You moved the royal warrant holders. Exactly as predicted."
Atem exhaled quietly.
"…So what I meant as a bridge between the afterlife and the living world has somehow turned into a bridge between all the world's aristocracies."
"A natural result. When you move, the world moves. Same principle as a mathematical theorem."
Seto's mouth curved, barely.
"And this many diplomatic engagements. But — it might be just the right thing."
"I know what you're thinking. I am your partner, but right now we're in the middle of official duties."
"Official duties or not, we're still us. Why not call the diplomacy a honeymoon?"
Atem smiled as he said it.
"I knew that was coming. You… there's a limit to how much you can mix the official and the personal."
"The mixed version is more efficient, isn't it?"
"…I see. For us as we are now, that may actually be the efficient option."
The party made its way through country after country — from kingdoms crowned in gold to empires of sand, to courts of ice.
Wherever they went, every eye in the room found only two people.
When word spread that "the quantum marriage king and his husband have arrived," crowds spilled into the streets and the press sent drones into the sky.
A brief rest in a courtyard, between engagements.
Seto and Atem sat beside a fountain.
Atem gave a small laugh.
"…Time alone with you always comes in this shape."
"It's not bad."
Seto answered immediately.
"You're here. That's enough."
At those words, Atem's expression softened just slightly. He stood — and, following the afterlife's form of greeting, moved to touch Seto's forehead with his own. That was the moment.
"Your Majesty Atem—!"
"Mr. President—! Look this way, please!"
Voices flew; camera flashes fired in every direction at once.
Seto let his shoulders drop and murmured, low: "So it comes to this after all."
Atem gave a small shrug.
"Well — the world is offering its blessings. Not bad."
In that instant, their eyes met.
In the middle of the noise, stillness existed only in the depths of each other's gaze.
Japan.
As the two passed through the private gate at Domino Airport, the press flashes lit them up again.
The King and the President — returning from what diplomacy had quietly named their honeymoon.
By this point, the world's internet had already been buried in breaking news of their homecoming.
"…The air at home really is the best."
Atem said it, pulling off his suit jacket.
Seto straightened his collar and replied, without warmth:
"It's less home and more returning to the eye of the next storm."
"Something's going to happen again?"
"…Yes."
Seto's gaze moved to the display. On it: the top trending news from the country's largest outlet.
"Quantum marriage couple returns home! The King of the Afterlife and the corporate king — what miracle comes next?"
A headline that seemed to be goading the future. Seto exhaled, without a word.
At that moment, the intercom sounded.
Before A.R.E.S. could respond, Atem's phone buzzed.
On the screen: a familiar pink logo.
That Magazine — Editorial Department
Atem looked at the screen — and his eyes lit up.
"Seto! It's a honeymoon feature!"
"…What kind of trip?"
"A honeymoon. They want to introduce the countries we visited in the pages of the magazine as 'forms of love.' Couldn't be more fitting, could it?"
Seto pressed two fingers to his temple.
"Diplomacy is official business. It is not a tourism brochure."
"But their intention isn't wrong. Wouldn't it be worthwhile to see how the living world receives love and theory?"
"Don't move again. …Every time you move, the world moves."
Atem only laughed, lightly.
"That too is destiny, perhaps."
In the depths of that smile, the King's instincts may have already been at work.
The knowledge that the phenomenon called 'the quantum marriage journey' — following love and theory — was about to sweep the world.
Several days later, the magazine's special feature title was announced.
On a pink background, gold lettering on the cover read:
"Love That Travelled the World — The King and CEO's Honeymoon Diplomatic Journal"
Within one hour of preorders opening, the first print run of one hundred thousand copies had sold out completely.
Atem, with evident satisfaction, suggested to the editorial team that they "make it available in the afterlife too."
And beside him, Seto muttered: "After all… this world moves on advertising rather than love."
But both of them understood.
The reason the world moved was neither theory nor advertising.
It was the undeniable quantum reaction of love and theory — in other words, their own existence itself.
Several weeks after the pink-covered magazine sold out worldwide.
Before the heat of the launch event had even cooled, the editorial department contacted Seto and Atem again.
"The response to the feature has been extraordinary — we'd love to do a spinoff!"
The proposal document had a glittering cover emblazoned with the words: "'Quantum Marriage' Sees the World's Love."
This time, on-location coverage — which meant, again, a travel feature.
The moment Seto read that line, he visibly narrowed his eyes.
"…So you want to drag us around the world again."
"It's not dragging, is it? But… I think it's a good idea."
Atem turned the pages and smiled.
"It's subtitled 'Honeymoon Edition.' Couldn't be more fitting for us."
"After diplomacy, now tourism. …Does the world have nothing better to do."
Even as he said it, Seto agreed.
With conditions.
"We take the photographs ourselves. No accompanying staff. Ordinary humans cannot enter the afterlife."
"…The afterlife?"
And there it was.
Around the same time, what arrived in Kaiba Corporation's official correspondence inbox was an official document from the Afterlife Public Relations Bureau.
The envelope's address was written in golden hieroglyphs:
"We welcome the King's return. We hereby request that the afterlife be selected as the destination for the honeymoon."
Atem's eyes lit up.
"Seto — the afterlife is inviting us too! This is destiny!"
"…So they read the magazine."
"They did. Apparently the data reached the afterlife's royal library as well. It says here they were deeply moved."
"Which means the magazine's distribution has now extended to the afterlife."
Seto exhaled deeply.
"Then my condition is one. I run it. No interference."
Atem smiled, delighted.
"Of course. With you there, wherever we go becomes the finest of journeys."
And so, on the third attempt, the honeymoon finally began.
When they set foot on the afterlife's ground, what awaited them was a dozen or more priests.
White robes with gold embroidery. Cameras at their chests. Lights in their hands.
Unmistakably: a film crew.
"Your Majesty, welcome home! Here are the 'photography locations' aligned with your itinerary!"
"…Photography locations?"
"Yes! On the orders of the Afterlife Public Relations Bureau — 'record the King and the royal consort's visit!'"
Seto immediately cut in, voice low.
"Photography is unnecessary. We handle it ourselves."
"B-but—"
"Our love and theory is not a subject to be photographed. It is a phenomenon."
The priests nodded as if instantly enlightened, breathed a reverent "…as expected of quantum marriage…! Precious!" — and from that point on, moved with them as silent support staff, shadow-like.
At every destination, the temple doors opened to cheering crowds. Along the afterlife's streets, banners reading "Welcome Quantum Marriage Honeymoon!" were lined up in rows.
At the baker's entrance, the flower stalls, in the hands of the afterlife's children — that pink-covered magazine had been distributed everywhere.
"…The entire afterlife is a readership."
"That's a good thing."
"No — it's alarming. Atem, when did you bring these in…"
While Seto murmured to himself, Atem laughed and answered.
"This is the circulation of civilization, Seto. The afterlife and the living world, past and future — all connecting."
And that night.
On the terrace of the afterlife's royal palace, before a sea of sand that glittered like stars, a moment of privacy arrived for just the two of them.
"…It's quiet."
"Because you said 'no interference.'"
"Hmph. Now, at last, it feels like a honeymoon."
Atem gave a small laugh and settled close beside Seto.
The afterlife's breeze passed gently between them.
A room in the afterlife's royal palace.
The morning after the banquet celebrating the King's return, Seto and Atem were led out by the priests for something called a "special inspection."
They followed a corridor of white stone, and emerged into a courtyard where people stood in neat rows, incense burning, a sweet fragrance drifting through the air.
At the center, a priest raised his voice.
"Your Majesty, and the King's Royal Consort! Beginning today — the ceremony of afterlife-style hospitality!"
"…Atem. What is this."
Seto asked without moving a single eyebrow.
Atem answered, chest out, thoroughly proud of himself.
"O-mo-te-na-shi."
"I thought as much. …You arranged for this again, didn't you."
Seto's eyes narrowed — just barely.
"Those who were moved during the last 'café afterlife inspection' apparently prepared this on their own initiative."
"The phrase 'on their own initiative' has rarely felt less convincing."
Atem laughed, entirely unbothered.
"But it's not bad, is it? The afterlife's people welcoming the King and the King's partner is a cause for joy."
Dishes, flowers, and music arrived one after another.
Smoke from incense burners swayed like threads of gold. The air took on a soft luminescence.
In the middle of it all, Atem narrowed his eyes with quiet pleasure — and murmured:
"…Seto. I want to open a sa-ten here."
Seto was silent for just a moment. Then he breathed in, slowly.
"…That would be work. Not a holiday."
"No, as part of cultural exchange between the afterlife and the living world—"
"Which means work."
"…I see."
Atem laughed and backed off cleanly.
Watching him, Seto thought to himself: when he gives in this easily, it actually makes me more uneasy.
The final day of the journey.
The priests lined up in neat formation before the two of them.
A priest held out a stone tablet.
"A record of Your Majesty and the Royal Consort's stay. All data organized — footage and stills both fully catalogued."
"…You were filming after all."
Seto's voice carried half a note of resignation.
"Rest assured — we are registered as an official photography unit."
The priest puffed up his chest.
"And furthermore…"
Another scroll was presented. On it, the words: "Unofficial Photography Materials."
"These were taken voluntarily by the citizens…"
Seto pressed two fingers to his temple.
Atem, meanwhile, leaned over the screen with evident warmth.
"Look, Seto. The angle is excellent. The light is perfect. …The afterlife's priests are talented."
"…Too talented. On the level of a surveillance network."
"But isn't it proof of how much we're loved?"
"What you have at this point is closer to a religion."
Atem gave a light laugh and held the data with care.
"Like king, like subjects."
Seto murmured quietly —
"Whether to accept it or to educate them… it's a difficult call."
— and considered it, half in earnest.
Above the afterlife, golden light drifted slowly in, shining as if to see the two of them home.
Back in the living world, the two carried with them the footage and stills the afterlife's priests had carefully compiled.
When they handed the data to the editorial department of that pink-covered magazine, the editor-in-chief's eyes literally lit up.
"W-what is this quality…!"
"The lighting is perfect, the composition is perfect, the expressions on both of you look like a scene from a film…!"
The photography credit read: "Afterlife Priest Unit."
For a moment, every member of the editorial staff nearly asked, "Which production company is 'Afterlife Priest'?" — but immediately understood there was no point in asking.
The magazine published that issue as a major special feature.
Thick with pages, a gold foil-stamped title on the cover:
"Honeymoon — Afterlife Edition: Love & Logic, and Eternity"
From the moment it went on sale, bookshops descended into chaos.
Pre-orders and in-store stock both vanished in moments.
The online shop went down temporarily under the traffic.
Within the same day, tens of thousands of signatures for a reprint had been collected.
Several days later, the editorial department called again.
"We'd love to make a photobook from this!"
The editor-in-chief's voice on the call was a mixture of excitement and barely suppressed tears.
Seto held the phone to his ear and pressed a finger to his forehead.
"…At this point, you've drifted considerably from that magazine's original concept."
"No — that's not right, Seto."
Atem, sipping herbal tea beside him, spoke with the serenity of a saint.
"They've understood it instinctively. That love and theory is, at its core, an eternal theme."
"Don't reframe it as philosophy."
Atem continued.
"Put behind-the-scenes shots in the photobook. Readers want to see what's underneath."
Seto narrowed his eyes immediately.
"Every time you try to show what's underneath, the world gets louder."
"But sincerity is something a king needs too."
"Your sincerity is always the broadcast variety…"
Seto exhaled quietly at the unstoppable Atem.
Stopping him is pointless. He'll take the photos regardless.
And so the day of the shoot arrived.
Atem held the camera and had Seto in his sights.
But this was Seto. He didn't miss the single unguarded moment when Atem leaned into the viewfinder.
A shutter sound.
By the time Atem looked up, Seto had already finished his own shot on his personal terminal.
"…You just took one, didn't you."
"I simply documented a hardworking employee at his duties."
"Then I'll fulfill my duty as a partner as well."
Atem pressed the shutter again.
The gesture was somehow triumphant, light, entirely like a child.
The photograph showed Seto's profile — softly smiling.
Perfect composition. Beautiful light.
Atem submitted it to the editorial team without hesitation.
Seto's camera, meanwhile, had captured Atem — cheeks slightly relaxed, shoulders loose, entirely unguarded.
So disarmingly endearing that Seto spent several minutes looking at the image before quietly moving it to a separate folder.
"…This one stays private."
And so,
"Love & Logic — Afterlife Honeymoon: Behind the Scenes"
became a topic of conversation before it even went on sale — and sold out again, instantly.
Atem said, with evident satisfaction:
"Seto — the behind-the-scenes shots were the right call after all."
Seto closed the magazine and answered, evenly:
"What was needed was your self-restraint."
Atem laughed.
"That, apparently… exists neither in the afterlife nor in the living world."
Seto gave a small laugh at those words.
"I know."
And left it at that.
