The story had ended.
Ezra took a deep breath and composed his frayed nerves. He could not afford to show a flustered demeanor before his patient.
He was a man who prided himself on having met tens of thousands of patients and gazed into the darkest abysses of the human mind. Yet the story the young man recounted so calmly was directly undermining the very foundations of the scholarship he had built over a lifetime.
He looked at Seoha and asked.
"Mr. Yu, among historical figures, there is someone whose experience closely mirrors your own case. Do you know who it is?"
"Reading John Nash's biography, I did think my situation was similar."
Ezra nodded.
The real-life inspiration for the film *A Beautiful Mind*, a genius mathematician who won the Nobel Prize for game theory. He had suffered immensely for decades from schizophrenia. He was also the most representative case demonstrating the relationship between mathematical genius and mental illness.
"His life can be summarized as a life-or-death struggle with inner voices. He received a formal diagnosis at age thirty, but you would know, wouldn't you? Intelligent people are reluctant to go to the hospital. Especially for psychiatric issues."
Seoha's face turned red.
He too had never once considered going to the hospital.
"I believe he experienced auditory hallucinations from his teens, or at least from his early twenties. In males, it typically begins around age fifteen and peaks around age twenty-five."
Seoha gauged his own age and symptoms. He concluded that the statistics matched to a considerable degree.
"And that period was—"
For a moment, the room fell silent.
Looking into Seoha's eyes, he slowly continued.
"John Nash's academic prime."
"Ah..."
"It was during that period that he established the equilibrium concept in game theory and produced innovative results in manifold theory. He received the Nobel Prize at age sixty-six, but that was a belated tribute to the achievements he had made in his twenties. Between those points lie over thirty years. No one ever talks about that."
Seoha nodded with a gloomy expression.
"It was time he needed to separate reality from hallucinations."
"Exactly. He spent decades trying to convince himself that he heard nothing. But you are different."
Clack.
Ezra removed his glasses and set them on the table. A strange fervor glinted in his eyes.
"From a psychiatric perspective, the status you granted Deoki is not a hallucination. You made it into an independent ego and concentrated the areas that place the greatest burden on your psyche onto it. Afterward, the main body named Yu Seoha became able to focus on logic and social function. An allocation so efficient it sends chills down one's spine. Was it a calculated choice?"
Seoha shook his head.
"I simply wanted to keep doing the math I loved."
He looked at Seoha with deep eyes.
The primes of geniuses who left their names in history are short.
Newton, Einstein, Gödel, and even John Nash and Alan Turing. They all produced their life's achievements in their twenties.
This is a topic widely studied in modern medicine, and the hypothesis that brain functions have not fully solidified until the early twenties has gained considerable persuasiveness.
'How long will this young man's prime last?'
The answer was simple.
Until the brain circuits responsible for his creative thinking were severed.
"But remember this. The more complex a role Deoki takes on, the greater the influence that ego's changes will have on you. And if the relationship between the two of you breaks down, no one can predict what consequences it will bring."
Whish—
The cold dawn wind cut through his collar.
Seoha walked back toward the hospital, huddling tightly. Seoul's brilliant neon signs reflected in the rainwater pooled on the ground, glittering.
"All my questions have been answered."
That was why he had sought Ezra.
His relationship with Deoki was changing. The contract he had made with it now would not last forever either. Seoha had wanted to know in advance the worst situation that could befall him. And what he should do when that time came.
Even after Seoha left, Ezra could not rise from his chair for a long while.
Because his conversation with Seoha had left a deep, lingering impression.
"Mr. Yu, before you leave, let me ask one thing. What do you fear most? Is it the disappearance of the genius within you, like John Nash?"
Ezra was inwardly convinced.
The ears that heard the voice of God going deaf, the eyes that saw the principles of the universe going dark, the sense of loss from plummeting into an ordinary human being. How could a person endure such a tragedy?
He paused, hand on the doorknob, then slowly turned his head to look at Ezra.
"No, Professor. I am not afraid of such things at all."
"Then what?"
"That something will go wrong with my head and I will lose my memories. That I might end up hurting the people precious to me."
"Even if that astonishing intuition disappears?"
Seoha shook his head and gave a faint smile.
"I don't think that would be a reason for me to quit math. Math is not the exclusive domain of geniuses. Countless scholars who walked this path in the past have proven that. I too am surely just one of them. And..."
"Is there more?"
Seoha swallowed the words that were about to come out.
"No."
Saying "It's merely a matter of time; with logic alone, I can reach the same results anyway" could sound arrogant.
Ezra stared at the closed door for a long time.
Just like every other part of our body, the brain is a consumable whose function deteriorates with age. This is a medically proven fact.
'There were exceptions.'
There are rare examples of geniuses who maintained their prime for an extended period.
Euler and Gauss.
For a long time, researchers classified these two as exceptional cases and buried them deep in footnotes.
'Now the distractions will decrease.'
These were Euler's first words upon hearing he would lose his sight forever.
And in the seventeen years between his blindness and his death, he produced half of all the papers he wrote in his lifetime.
How?
Psychology has a concept that can explain this.
Csikszentmihalyi's Flow theory.
He devoted his life to answering the question, "When are people happiest?"
In Flow theory, he states that humans are happiest at the moment when their abilities and the difficulty of a task match perfectly, achieving complete immersion.
Scientific data support that the ecstasy this provides does not consume the brain. Perhaps those two great mathematicians lived their entire lives in such a state.
A divine blessing of a realm reachable only when century-level mathematical talent is combined with an innate personal temperament.
In the expression of Seoha, who had asked what was so terrible about losing one's talent, Ezra saw a third exception.
Of course, genius on the level of Newton and Ramanujan is accompanied by psychiatric side effects.
This might also be why the achievements of Gauss and Euler leaned more toward scholarly synthesis than toward the creation of new concepts.
But Seoha is different.
The highest level of creativity and endurance. He might be the first mathematician in history to possess both.
"Perhaps his entire life will be his prime."
He laughed in a low voice.
* * *
"Ahh! I want to be discharged."
Having lain in the hospital bed all day, his inner thoughts had burst out before he knew it.
"Oppa, are you struggling a lot?"
Seoeun stopped peeling the apple and looked at Seoha with worried eyes.
On the plate sat an apple, crookedly and thickly peeled, reduced to half its size.
"No!"
Seoha quickly sat up and speared the apple with a fork.
"I'm perfectly fine; it's just frustrating being told to lie around."
"Where did you go last night?"
Seoha's hand paused briefly.
Seoeun was clearly worrying about him excessively. It troubled him that she was staying in the hospital room instead of going to school.
"I had some business to take care of. But isn't the IMO training camp starting soon?"
"I'm not going, though?"
"Huh?"
"My brother is sick; where would I go?"
Seeing Seoeun continue peeling the apple with a calm demeanor, Seoha let out a small sigh.
"It's nothing serious. I'll get better after a little rest. Healthy people collapse from overwork or anemia too."
"It wasn't, though?"
Seoeun continued speaking without stopping her hand.
"Syncope from anemia has prodromal symptoms. Dizziness, nausea, tinnitus. You didn't have any of those."
Seoha's eyes went wide.
"How do you know that?"
"That."
Seoeun gestured with her eyes toward the corner.
A book lying on the attendant's chair. It was a medical encyclopedia he had bought when he was young.
"I read it all here. You're in a state where even the doctors can't find the cause right now, aren't you? So you have to wait quietly until the detailed test results come out."
Seoha rolled his eyes. Not a single word was wrong.
"Yeah. I will."
Seoeun's expression brightened radiantly. Watching her, Seoha fell into thought.
'I need a way to reassure her.'
Her saying she would give up on the IMO was likely not a joke. In strange ways, Seoeun took after him, and her stubbornness was no small thing.
He thought showing her directly would be better than trying to persuade her with words.
"Seoeun, want to go out?"
"Huh? So suddenly?"
She seemed surprised, but showed no sign of disliking the idea.
Come to think of it, he had barely spent time with his younger sister lately. Though the doctor made a troubled expression at the consecutive outing requests two days in a row, the two managed to leave the hospital safely.
"Is this Daehangno?"
"Yeah."
There happened to be many things to see nearby.
The smell of tteokbokki sold on the street, an amateur singer performing, people's lively laughter. It was the kind of place that made you happy just walking through it.
They bought hot dogs, one each, and walked slowly down the street.
It was a pleasant time.
After making a round of Daehangno and preparing to return to the hospital, Seoeun's gaze fixed on a stationery store window.
"It's a fountain pen."
"Yeah, the same one Oppa uses."
Jingle.
Seoha went inside and handed Seoeun a fountain pen that differed from his only in color.
"Do you like it?"
"Ehehe!"
Seoeun hugged the box, grinning broadly, overjoyed for some reason.
Getting out of the stuffy hospital room had cleared his head.
Click.
Like a locked faucet being opened, his thoughts began to spin fiercely.
Seoha stopped walking and stood stock-still in the middle of the street. Seoeun turned around, puzzled.
'Something changed?'
Complex geometric structures were transparently overlaid upon the scenery before him. He felt he could convert people's movements into vector values. Even the streetlamp light looked like the graph of a wave equation.
This was something he could only do when together with Deoki.
The eighth step of the hypothesis that had suddenly come to mind.
Back then, merely glimpsing the essence of the problem had felt like his head would burn up. But now that his brain could function fully, the cogwheels of thought meshed and turned without the slightest sense of dissonance.
"Oppa?"
'Ah!'
Seoha hurriedly returned to reality and smiled at his sister.
That very thing he had felt on the day the contract with Deoki was completed. Seoha could finally feel in his very bones the true nature of the liberation he had only sensed vaguely until now.
Was it because this time was enjoyable?
A feeling of nerves smoothly relaxing and settling back into place.
'I can break through the eighth step.'
"Let's go back to the hospital room."
"Yeah!"
Seoeun subtly reached out and took Oppa's hand.