Atem makes a horrifying discovery.
Despite already being legally, socially, and quantum-mechanically married to Kaiba Seto...
...he has never properly been proposed to.
As the self-proclaimed founder of the Theory of Love, this is clearly an unacceptable gap in the data.
With the help of romance magazines, AI simulations, and an increasingly elaborate strategy titled 'Project Proposal Trigger', Atem prepares the perfect plan to make Kaiba propose—logically, romantically, and completely according to theory.
Unfortunately for him, Kaiba has already predicted every move.
What follows is an evening where logic yields to emotion, a proposal that no algorithm could fully calculate, wedding rings engraved with an unsolved code that fascinates the entire world, and one final conclusion:
Some equations are never meant to be solved.
Some answers only exist when two people stand together.
Answer =
This is a translation of an original work on Pixiv.
Original Title: 愛と理論 25 愛と理論
Original Author: 葉人(@Hathor₋yuki)
Personal site: https://prideshipping.sakura.ne.jp
The terrace of the Kaiba mansion.
The stars gleamed as if connecting the boundary between the afterlife and the living world.
Atem tilted his glass of fruit wine, and his eye happened to catch a feature page in the magazine.
On the pink cover, gold lettering read:
'Special Feature: The Most Romantic Proposals in the World'
"…A proposal."
The words had left his mouth before he knew it.
The fingers turning the page went still.
Flowers, a ring, a night view, words of vow.
And then, one decisive line:
'Whatever the relationship, it's important to give love's pledge a form.'
In that moment, Atem realized something.
"…Seto, we're quantum-married, aren't we?"
"We are. Legally, socially, theoretically—already perfect."
"But… you've never proposed to me."
Silence.
The ice made a small sound against the glass.
"……At this point?"
"I just realized it."
Seto pressed his fingers to his temple.
The same expression he wore when receiving a report that an AI had gone rogue.
"You've… only just arrived at that conclusion."
"Yes. As a result of studying the theory of love, as a king."
"…As a result."
Atem kept his serious expression and took a sip of fruit wine.
"Seto, I believe I—as the founder of love's theory—should be proposed to."
"You're being bound by a theory you founded yourself."
Seto's perfectly composed retort went straight past Atem, who remained entirely earnest.
"In other words, for the further development of love's theory, an experiment is required."
"…Another experiment. I did propose, didn't I."
"No—that was addressing the resolution of the 'Near-Proposal Incident'."
"Stop being serious about the wrong things."
Atem was, in essence, always serious. It was simply that the angle of that seriousness tended to run slightly off-center.
And with a straight face, he declared:
"I'm going to devise a plan to get proposed to."
"Wait—who's the test subject."
"Who else could it be."
Seto looked up at the sky. He had proposed—technically. He had made and given the ring.
The 'founder of love's theory' remained, as ever, magnificently at his own pace.
Before the communication terminal connecting the afterlife and the living world, Atem's expression was grave.
The tip of his finger scrolled to a feature in the pink-covered bridal magazine.
'Make Him Say It ♡ — 10 Methods for Drawing a Proposal Out of Him'
"Hmm… 'make him say it' means intentionally steering the other party while appearing to respect their spontaneity."
Atem nodded to himself.
His eyes had already entered full strategic planning mode.
Beside him, the AI LOVE-OS chimed to life.
"Atem-sama, shall I construct a proposal-inducement strategy?"
"Begin construction. Theory first. Emotion can wait."
The founder of love's theory prioritized logic for the sake of the operation.
"Subject: Seto-sama. Personality data: logic-driven, rationalist, restrained in emotional expression—but strong possessiveness. To increase success rate, 'compatibility of theory and emotion' is required."
"Meaning I must be 'theoretically romantic.' …A difficult challenge."
Atem folded his arms and considered for a moment.
Then he looked back and forth between the magazine spread on the desk and the AI's display.
"Recommended approach ①: Stimulate Seto-sama's intellectual curiosity and engage in a logical discussion on the definition of a proposal."
"Recommended approach ②: Invoke an ancient royal ritual and request 'a modern vow' in its place."
"Recommended approach ③: Deliberately engineer a romantic situation (examples: twilight, flowers, light)."
"③ is environmental manipulation. Too contrived to leave to an AI. Seto is a man who loves theory. We start with ①."
"Logic-induction type: approved. …Target launch timing?"
"The next time we meet. Under the guise of a natural flow of conversation, I'll ask him 'what is a pledge of love.'"
"Approved. Note: if you speak first, there is a risk the other party will 'analyze the response theoretically' and that will be the end of it."
"…In other words, exactly as usual."
The King exhaled softly.
But in his expression, unmistakably, was fighting spirit.
"Addendum: according to Seto-sama's psychological model, he has a tendency to be vulnerable to 'the unexpected.' Therefore, stimulating the emotional domain via 'sudden action' is effective."
"The unexpected… a surprise attack, then."
Atem's eyes lit gold.
The face of someone who had just conceived a new strategy in the middle of a duel.
"Conclusion: Operation name, 'Project Proposal Trigger.'"
"Atem-sama, current success rate: 67%."
"Good enough. Neither theory nor love can evolve without practice."
Atem stood and looked up at the stars flowing behind him.
"Seto… look forward to the next experiment."
"※ Warning: the other party may preemptively deliver a theoretical counterargument."
"※ Suggestion: combine with 'non-verbal interference' via eye contact and a smile."
"Yes. Eye contact and a smile… I see. 'Silent strategy' is also part of love's theory."
"Indeed. It is commonly called 'speaking with one's eyes.'"
"A fine phrase."
And Atem slowly closed his eyes.
The full shape of the strategy assembled itself, perfectly, in his mind.
The next time they met, love's theory would evolve into proposal theory.
Laughing inwardly at that thought, Atem wore an expression that was, just slightly, villainous.
Standing before Seto's door, Atem closed his hand into a fist at his chest.
The AI-crafted 'ideal proposal operation' was perfect.
Lighting, music, script, expression.
Every variable had been calculated to produce a theoretical success rate of 100%.
All that remained was execution.
But the moment he opened the door, Atem stopped.
There was Seto—arms folded, waiting, as if he had foreseen exactly this.
Not smiling.
And yet his gaze said, unmistakably: 'I know.'
"Atem… the AI put you up to this, didn't it."
Before Atem could respond, Seto picked up his coat.
"We're going out."
Their destination: the top-floor lounge of Kaiba Corporation's finest hotel—the same place they had gone on their first date.
The glittering night view of the city.
A floor reserved entirely for them.
A sea of light, as though the stars had descended to their feet.
The moment Atem opened his mouth after they were seated, Seto set down his glass and spoke—low, unhurried:
"In theory, love is a phenomenon that resists definition. But when I met you, I chose to accept that margin of error. You are the first thing I have ever found beautiful precisely because of its contradiction. …Live alongside me from here on, with all of quantum's uncertainty included. Atem."
His voice was quiet—and a reality as certain as anything could be.
For a moment, Atem said nothing. He only looked.
The 'operation' to orchestrate a formal proposal—to have it delivered with precision—shattered completely. But no better outcome existed.
The happiness registering in Atem's expression overflowed lightly past the upper bounds of the AI's measurement range.
The observing AIs logged 'incomprehensible emotional response' in unison and went silent.
Seto gave a wry smile and poured the wine.
"What's wrong? Any theoretical objections?"
Atem shook his head, faintly.
"…None. Only that my definition of happiness has changed."
Their theory was updated by one more entry.
On Atem's finger, a slender, precise platinum band caught the light.
From a pair ring, to a wedding ring.
It was not mere decoration—it radiated a presence that the world recognized instantly as proof of the quantum marriage.
Atem's eyes were drawn to it, again and again.
In the office, during interviews, at diplomatic meetings—his gaze kept returning there.
Everyone understood.
'Something had happened.'
Naturally, the first to catch the scent was the pink-covered bridal magazine.
The editorial team, in their familiarity, went so far as to pursue a direct interview with the man himself.
Atem was not accustomed to press interviews.
Let alone while still adrift in the afterglow of a proposal.
Every last piece of information was taken from him.
"What happened, Your Majesty?"
"A proposal…"
"A proposal!?"
A quantum-married couple—proposing now, of all times.
But there was no way they would let a story like this pass.
"What were the words of the proposal?"
"Let me think… Seto said something… theoretical…"
"What kind of theoretical?"
"Well… I don't actually remember."
He didn't remember. And yet the editorial team lit up immediately.
'The King Who Loved So Deeply He Forgot the Proposal.'
The sound of a tagline clicking into place.
But what excited them most was the 'mysterious cipher' engraved inside the ring.
What Atem innocently showed them had a syntax no one could decode, and before long it had drawn in mathematicians and cryptographers alike.
Without Atem knowing, a project titled 'Crack the King's Ring Cipher' was launched—and ultimately, only one thing was confirmed.
Not enough clues.
And a hypothesis was put forward: 'It cannot be solved without the other ring.'
In other words, the two rings together formed a single key.
A complete and distinctly Seto-like arrangement—physically proving love's theory.
Atem knew none of this, and simply kept saying: 'Seto was too wonderful for words.'
"…I remember it."
Seto's quiet laugh—and the AIs, the editorial team, and the world all fell silent for just a moment.
Love's theory continued its steady updates.
After the inscription was pointed out, Atem had begun to sense that the indecipherable string of characters held something within it.
And his instincts—too sharp for his own good—told him: the missing clue must be hidden in Seto's ring.
The 'mysterious cipher' the bridal magazine had found was, according to quantum physicists, unmistakably a pair—two halves forming one whole.
Which meant the other key was in Seto's ring.
Something in Atem stirred—the blood of a king, or perhaps a duelist.
'I have to decode it.'
Seto, of course, had seen this coming entirely.
"Stop trying to look at my ring."
"Why?"
"If you know, the world will know. The world isn't ready for that theory yet."
'The world is not yet ready to handle love and theory.'
But the world did not stop.
Decoding teams. AI analysis units. Even children became consumed by the 'ring cipher'.
Hashtags danced across social media.
#LOVELOGICCODE
#KAIBA_RING_THEORY
Scholars attempted to formalize love as an equation. Couples began encrypting the insides of their own rings. A trend was born: proposals, marriage certificates, everything preserved in cipher.
In time, it became known that the origin of this global cipher fever lay at Kaiba Corporation.
Atem had moved the world with love. And now Seto had moved the world with theory.
Months passed, and everyone came to understand the same thing.
No hypothesis, no matter how carefully constructed, could solve it without a hint. But the word that would finally emerge—everyone sensed it would be the same.
Atem needed to know.
The inside of Seto's ring. The answer to the cipher.
The whole world was in an uproar over it, and he—the very person it concerned—didn't know.
That situation sat uneasily with him, as both a king and a partner.
"Seto, that cipher—"
The moment he reached out, Seto said quietly:
"Do you believe a day will come when you take off that proof?"
At those words, Atem's hand stopped.
Something deep in his chest ached, faintly.
Taking off the ring. That meant an ending.
An ending was something he had no wish to even imagine.
Seto held out his left hand, calmly.
"If you want to see, look."
Not a provocation. Simply permission.
But Atem found he could not even touch that ring.
Silence.
Between the two of them, a quiet happiness filled the space.
"…I'll leave it."
Atem murmured, softly.
"Let this mystery remain unsolved."
All they needed was their own love and theory. Atem smiled.
Seto smiled too.
"That's the right answer."
That night, the two of them stood together by the window, looking at each other's reflections in the rings.
As if the unsolvable cipher were pledging eternity.
The AIs quietly stopped recording—and added one more piece of unsolvable data to their logs.
'Answer = Love and Theory'
