Atem finally discovers the modern concept of a de facto marriage and is delighted to learn that, apparently, he and Kaiba already qualify.
Unfortunately, the rest of the world discovers this at the same time.
What begins as a bridal advertising campaign quickly escalates into magazine covers, international headlines, academic analyses of their relationship, and a mysterious new social phenomenon known as Quantum Marriage.
According to Atem, their relationship exists in a quantum state: impossible to define until observed, yet undeniably real.
According to Kaiba, everyone has completely lost their minds.
As media outlets, social networks, and even the afterlife struggle to explain the pair's impossible partnership, Atem and Kaiba continue their greatest ongoing experiment: the daily operation of love.
Or: two men accidentally become the world's most famous married couple without ever actually getting married.
This is a translation of an original work on Pixiv.
Original Title: 愛と理論 06 王、量子婚をぶち上げる
Original Author: 葉人(@Hathor₋yuki)
Personal site: https://prideshipping.sakura.ne.jp
The trigger, once again: that pink-covered magazine.
Inside, he had found the term common-law marriage.
"…Seto. We qualify for this, don't we?"
"What are you on about. We've been that for a while now."
"I knew it! I finally understand it. Reading really does pay off."
"There's nothing to be proud of. How many issues have you gone through?"
But the moment the King of the Afterlife nodded with solemn pride at his newfound grasp of common-law marriage — someone from Kaiba Corporation's PR department was watching.
That afternoon, an internal memo made its rounds.
New Division Proposal — Bridal Business Department: Advertising Models — Kaiba Seto, President / Atem
"…Who authorized this."
"We felt that the President himself was the most suitable choice."
"I have no memory of that."
"Seto — it seems our love has become a form of social contribution."
"…Don't go expanding the definition on your own."
Even so, the projected advertising impact was undeniable.
In the end, there was no other conclusion: they were the optimal choice.
The moment word got out that the two would be shooting, social media erupted instantly. The pink-covered magazine posted its highest sales since its founding. And then came the breaking news:
Kaiba Seto and Atem — "Beyond Common-Law Marriage": The Ideal Partnership
From the afterlife and the living world alike, the congratulations did not stop.
Atem watched the coverage, leaning his head against Seto's arm.
"Seto — apparently we've moved well beyond seikatsu-kan at this point."
"…Fair enough. We're a social phenomenon now."
The photography studio.
Seto's mind was brighter than the white lights overhead — his eyes caught every crease in the backdrop paper without missing a beat.
"The lighting is off. Drop the angle five degrees. That shadow is half-committed."
"Y-yes, sir!"
He ran the calculations on light faster than any photographer could, settling on composition through pure logic.
Kaiba Seto was, at this point, less a subject being photographed than the director of the entire shoot.
Beside him, Atem was smiling — visibly, genuinely enjoying himself.
He held his ringed hand up to the light and asked the costume team, "Which civilization's ornamentation was this based on?"
"Seto — 'natural' is fine for this, right?"
"Even so-called 'natural' should not deviate from the golden ratio."
"So we're guiding nature with theory."
"That's exactly right."
The staff came to a quiet understanding.
These two speak of love through logic.
The shoot proceeded with an intensity no one had anticipated — Seto's precise direction and Atem's commanding presence layering together into something undeniable. On screen, the two were less models than the embodiment of a matched ideal.
Near the end of the shoot.
The photographer murmured, almost involuntarily: "…Could you move a little closer? So it feels like — love."
Atem glanced at Seto's profile and smiled, soft at the edges.
Seto held his gaze on the camera.
"Love is not something you feel. It's something you define."
"Then shall we keep running the experiment?"
The shutter clicked.
Every member of the staff knew, in that instant, that this was the shot. The one that would be on the cover.
"The Theory in the Green Room. The Equation of Love and Social Convention."
When the shoot ended and the studio lights came down, the room settled into the quiet that follows a battlefield.
The green room.
Seto at the mirror, loosening his tie. Atem still in costume on the sofa, leafing through the magazine's proof pages.
"'The ideal vision of a partner,' apparently."
"Too vague a definition. Ideal is contingent on individual scale."
"…But for them, it seems we are that ideal."
"You can't be serious. Who else could keep up with you."
Atem laughed and tapped his ring lightly.
"The social concept of marriage. In this civilization, they call it the basic unit of daily life."
"The basic unit of daily life. For a corporation, something like a merger."
"So we're co-directors, then."
"…Effectively, yes."
Silence.
Atem picked up one of the proof pages and held it toward Seto.
The headline read:
The Ideal Love Is Built on a Balance of Effort and Understanding
Seto raised an eyebrow — just slightly.
"Understanding can be reached through theory. But effort belongs to the emotional domain. That's where it gets complicated."
"Seto — you try to handle love through theory."
"That's my way."
"But I handle love as emotion. Which means ours is a dual-mode model."
Seto exhaled a short breath. A quiet laugh.
"The integrated model holds, then."
"The Unified Theory of Love. We could submit it to a conference."
Their laughter dissolved into the stillness of the green room.
Seto glanced at his watch and stood.
"We're going home. Next phase: the household as social experiment."
"And the results appear tonight at the dinner table?"
"If you're the one cooking."
"Then the experiment succeeds. The moment I pick up a knife, you step in to help."
The door closed.
What remained: the glow of two rings, caught in the mirror.
The coexistence of theory and emotion — that was the definition of love they had reached.
One week after the shoot.
On a quiet afternoon, Kaiba Corporation's PR department descended into a subdued panic.
"Sir, every trending topic right now is you — all of them!"
"'#IdealCouple' is number one worldwide! And, um — they're calling you a couple, sir!"
Seto, signing documents at his desk, said one thing.
"Any movement in the stock price?"
"It's actually going up, sir!"
"Then there's no problem."
A man who could weigh economics and romance on the same scale — that was Kaiba Seto.
Meanwhile, in the afterlife, Atem was surrounded.
"My King! Your marriage announcement is spreading through the living world's communication networks!"
"…Announcement? I didn't announce anything."
"But — 'official advertising models = official couple' is how they're reading it!"
"Ah. A civilizational misreading."
Watching the priests scramble, Atem calmly reached for his phone.
"So 'liking' something is the living world's ritual of blessing."
"Since it says 'like,' I suppose it must be…! The whole afterlife is rejoicing — 'our King is receiving blessings!'"
"That's a good thing."
Atem smiled, unhurried. On his finger, the ring Seto had made caught the light.
The Kaiba mansion.
A news program filled the television screen.
'The King' and the Modern King — A Love That Crosses Dimensions
Economic Analysis: What Brand Effect Does Their Relationship Generate?
"Can the theory of love be replicated? Our special feature, next."
The anchor read on.
"Seto — it seems we've become a special feature."
"Let them do as they like. There's no need to manage the narrative."
"So — our very existence is proof of the theory."
Seto's mouth curved, just slightly.
"…Then the next question is sustainable love."
"A fine phrase. Should we present it at a conference?"
"Put it in Kaiba Corporation's annual report."
Another laugh passed between them.
Whatever interpretation the world placed on them, to these two, the world had always been both laboratory and daily life.
The rings caught the light and shimmered.
Not icons. Not symbols. The proof of something that lived at the intersection of theory and feeling.
And on that day, the world arrived at an official understanding:
Love may not be explainable through theory — but if anyone can prove it, it's Kaiba Seto and Atem.
The living world. A hotel lounge, somewhere overseas.
Seto had his laptop open. Atem sat across from him, sipping coffee.
Both in suits. Every appearance of two executives before a board meeting — until the press burst in.
"Mr. Kaiba! And Atem! Could we have just a moment about the two of you—"
"I've never trusted the phrase 'just a moment.'"
"Ah — the living world's ambush interview."
"Sir! Since the campaign, the whole world has been calling you two the ideal vision of a partner—"
"It's a matter of compatibility, not emotion. The result of optimization."
"The ideal isn't something you seek. It's the sum of the effort required to maintain it."
"So you're saying you work at the relationship?"
"No. The definition of effort is different."
"For us, effort means continuing the conversation. Love is the process of not avoiding disagreement — of arriving at understanding."
The reporter was, completely, without words.
A few seconds passed. Another journalist ventured forward.
"S-so… do you two say 'I love you' to each other?"
"Love is less about definition than operation. We're currently in operation."
"Which means we're in the act of loving, right now."
The cameras stopped.
In that silence, Atem smiled warmly and continued.
"The interview ritual isn't unwelcome. But next time, we'd recommend making a reservation."
The press corps had no choice but to retreat.
It was no different in the afterlife.
Atem had barely shown his face before he was surrounded.
"M-my King… could we have just a moment—"
"'Just a moment' again. Nobody learns."
"N-no, we wanted to cover the ideal couple feature for the afterlife as well—"
"The afterlife has a news program now?"
"We launched one. Just recently!"
"I'll give you that — the initiative is admirable…"
"How would you describe your relationship in one word?"
"Quantum state."
"…Pardon?"
"Undefined until observed. But undeniably present."
The priest was left with nothing to say.
That night, a new word was born in the afterlife: quantum marriage.
No one, of course, had any idea what quantum actually meant.
Back in the living world.
Home. Ties loosened, jackets off.
"…That was a tedious stretch of time."
"But it was fun."
"For you."
"'Love in theory' — that might end up in the next feature."
"We should trademark it."
Their laughter dissolved into the night cityscape beyond the window.
Even in the middle of a media storm, nothing shifted.
Walking the line between logic and feeling, they continued, quietly, to operate their love — as they always did.
The living world. Afternoon. Kaiba Corporation headquarters.
"…'Quantum marriage' is trending number one."
At Isono's words, Seto blinked. Twice.
The display was filled with tags, end to end.
#LoveInTheory
#LoveInOperation
#QuantumMarriage
The news anchor read on.
"'A relationship undefined until observed.' Truly the ideal partnership for the modern age!"
"…Truly the chaos of the modern age."
"Sir, we're being flooded with requests for comment. There's an understanding that you were the one who proposed quantum marriage—"
"Who proposed anything. I was simply observed without consent. By someone who moves the world."
At that moment, a knock at the door.
Atem walked in, a pink magazine — that magazine — in hand, breezy as ever.
"Did you see? Our quantum marriage is moving the world."
"What's moving the world is your mouth. I'm on the side trying to stop it."
"But the outcome is favorable. A world where love is discussed through theory — genuinely amusing."
"…Atem, are you using amusing and chaos as synonyms?"
"The difference is marginal. But if the observers are happy, that's enough."
"So as long as I'm happy, the theory holds?"
"Naturally. If you're happy, love is confirmed at one hundred percent."
Seto exhaled.
"…Your probability calculations are romanticism dressed up as a bug in the system."
"Uncertainty is the very aesthetic of quantum mechanics."
Beside them, Isono quietly wiped his eyes. (Sir… you've transcended marriage and reached philosophy…)
Something similar was unfolding in the afterlife.
"My King — quantum marriage is the talk of the afterlife as well!"
"Ah, right — Nefer-Link."
"Through Seto-sama's network! But…"
The priests spoke in unison.
"We don't know how to celebrate a love that hasn't been observed!"
"You don't need to celebrate it. You just feel it."
"Feel it…!"
"So — the King is recommending feel-it marriage!"
"…Don't go coining derivatives on your own."
The living world. Night. The Kaiba mansion.
"…It's spread to the afterlife too, apparently."
"Yes. A good sign."
"I wouldn't call it good. There are reports now claiming 'the marriage registration has been submitted in a quantum state.'"
"Technically, no paperwork has been filed. But the heart has been observed."
"……"
Silence.
Atem took a sip of herbal tea and smiled, satisfied.
"Seto. A trend is the aggregate of people's desire to understand. If so, it's only natural that we — who resist easy understanding — stand at the top."
"…There's nothing to do but accept it."
"Accept what?"
"You. And this entire phenomenon."
Atem laughed, small and quiet, and nodded.
"That's the wisest choice. Love is most stable when it exceeds logic."
"…Instability as stability."
"Isn't that what quantum mechanics is?"
Conclusion.
At the center of the quantum marriage boom that swept the world and the afterlife alike, the two continued — quietly, today as always — to love each other, unobserved.
Night.
A soft light fell across the living room of the Kaiba mansion.
Atem sat on the sofa, tablet in hand, still smiling.
"Quantum marriage is still trending number one worldwide. Same in the afterlife, apparently."
"Hmph. Too many people attaching pointless analysis to it. 'A marriage that becomes valid upon observation.' 'Love where the wavelengths align.'…"
Seto picked up his herbal tea and sighed once.
Even so, his voice carried something — just slightly — softer than usual.
"Everything you touch starts to sound like a religion."
"And every response you give sounds like an academic paper."
Atem laughed and reached out, tracing the rim of Seto's mug with one fingertip.
Seto glanced away — and made no move to stop it.
"Even so. Everywhere I look, it's nothing but blessings."
"…Let them bless away."
"You look just a little pleased, you know."
"You're imagining things."
Atem gave a quiet laugh.
It rang warm in the air, and for just a moment, Seto let his shoulders drop.
"Seto. Whether in the living world or the afterlife — wherever I am, I'm beside you. That feels natural to me."
"Obviously."
"Obviously?"
"We're not the ones being observed, and we're not the ones doing the observing. We simply exist within the same equation."
"Heh… you've become a poet."
"It's theory."
Seto said it plainly.
But Atem's smile didn't waver.
And watching that steadiness, Seto's expression softened too.
"Here."
Atem lifted his ring slightly.
Seto raised his own to meet it, and the two bands touched with a small, quiet sound.
"This is our definition — isn't it?"
"…Yes."
"Then let's update it."
"Update it?"
"From quantum marriage to confirmed marriage."
Atem's voice was half a joke and entirely serious.
Seto was silent for one beat — and then laughed, low.
"When you say it, physics genuinely weeps."
"But you laughed."
"…I'll grant you that. It's a complete breakdown of logic."
They laughed together, and then settled into stillness, close.
Fingertips touched. Two temperatures confirmed each other, overlapping.
Outside, quantum marriage was making headlines.
But this space was neither observed nor recorded.
Only real — held inside a definition that belonged to the two of them alone — as the night continued, quiet and unhurried, sweet and certain.
