Now that the issues with his own body were on their way to being resolved, Jin decided to seize the moment and consult No. 700672 about another lingering concern.
"There is one more thing," Jin said. "Do you happen to know anything about Mana Overload Syndrome?"
"Mana Overload Syndrome? Inferring from the name... I assume you mean a physical ailment caused by an excessive accumulation of mana?"
"Yes, exactly."
Mana Overload Syndrome—the affliction plaguing Elsa Randol, the young woman Jin now considered his sister figure.
While she was currently living a normal life thanks to the mana-absorbing bracelet Jin had crafted for her, that was merely a symptomatic treatment. A true cure remained elusive. Along with a way to stop an Ether Stampede, Jin had been searching for a solution to this syndrome for a long time.
"Hmm... I believe I have some idea," No. 700672 replied.
"Really?"
"Indeed. Tell me, do you know how free ether is converted into mana?"
"Yes," Jin answered. "It's processed by the magi-mitochondria within the cells, right?"
"So you call them magi-mitochondria... Correct. Within the cells of a magi, there are microorganisms that coexist in a symbiotic relationship to convert free ether into mana."
No. 700672 spoke with the tone of a teacher reviewing a fundamental lesson. Jin nodded silently, listening intently.
"When a magi performs magic, they draw in free ether from the atmosphere. Conversely, when magic is not required, the magi instinctively switches to a state of non-interference with the ether."
As the explanation continued, a spark of realization flashed through Jin’s mind.
"I see!"
"It seems you’ve grasped it," No. 700672 noted. "A patient with Mana Overload Syndrome continues to take in free ether even when it isn't necessary. In other words, they are simply poor at controlling the intake of free ether."
The true nature of the syndrome was finally clear. Now, all that remained was the treatment.
"And what is required to control free ether?"
"A... mental catalyst?" Jin ventured.
"Correct. Most likely, they suffer from a deficiency of mental catalyst within the body—specifically, within the brain. They have just enough to perform magic, but not enough to exert control over the free ether itself."
Jin fell into deep thought. Elsa was a top-tier practitioner of both Craft Magic and healing magic. Could she really be incapable of such control?
When he voiced this doubt, No. 700672 provided a concise answer.
"You are forgetting about the frequency."
That was it. The frequency of mana used to trigger magic was distinct from the frequency required to manipulate free ether. Jin felt a pang of self-reproach for overlooking something so fundamental.
"Of course. I completely forgot."
No. 700672 watched Jin with a faint, knowing smile. "Then I assume the treatment is obvious to you now?"
"Yes," Jin replied instantly. "The mental catalyst is the key."
"Precisely. Administering a mental catalyst should result in a cure with ninety-nine percent certainty."
A path forward had finally opened. However, one problem remained: Jin’s supply of the substance was quite low.
While he had discovered a similar substance in the underground cavern, he hesitated to give it to Elsa immediately. Even though he had identified it as a mental catalyst, the thought of something going wrong when it came to Elsa made him pause.
But after a moment’s reflection, he realized his anxiety was likely disproportionate to the risk.
"The dosage required would be extremely small, wouldn't it?"
No. 700672 nodded. "I mentioned before that extracting it from a living brain requires millions of subjects, did I not? The inverse is true for treatment. To prescribe it to a human, a dose as small as one-millionth of a gram is sufficient."
If anything, the challenge would be accurately creating a solution so incredibly dilute.
"What happens if the dose is too high?"
"A mental catalyst affects mana as well as free ether. The potency of one's magic would increase drastically—explosively, even. And the result of that would be..."
"The total exhaustion of internal mana," Jin finished. "Mana Depletion."
"Exactly. And that would present its own set of life-threatening problems."
"I understand. Thank you so much."
Jin felt a massive weight lift from his chest now that a permanent cure for Elsa was within reach. He still had about 0.1 grams of the mental catalyst he had previously received from No. 700672. That was more than enough.
"So, she just needs to drink a solution of it?"
"Yes. The mental catalyst will be absorbed through the stomach, enter the circulation, and eventually accumulate in the brain."
Jin let out a long, shaky sigh of relief. Elsa could finally be cured.
"Hmph. Judging by your reaction, is this patient someone very dear to you, Jin-dono?"
"Eh? Ah, yes. She’s a brilliant disciple, a gifted healer, and... precious family."
As Jin answered, he pictured Elsa’s face. Only Reiko noticed that his cheeks had turned a very faint shade of red.
With his major worries settled, Jin decided the timing was perfect to make a proposal he had been mulling over.
"Would you consider coming back with me?"
"To your home, Jin-dono?"
"Yes. My predecessor laid the groundwork, and I've developed it into a proper base. You would be able to recuperate much more comfortably there."
He didn't mention the name Hourai Island specifically.
"Hmm. I appreciate your concern for my well-being. However, as for me..."
"I know you need free ether to survive," Jin interrupted. "I have the means to provide that as well."
Jin looked at No. 700672 with earnest eyes, but the ancient being slowly shook its head.
"I am truly grateful, but I must decline."
"But why?"
"This place... it is where my master lived. I have a deep attachment to it. I have decided that when the time comes for me to perish, it will be here. Whether it is years or decades from now, when my life runs its course, I wish to stand still in this place of memories."
"I see..."
"Your offer and your kindness move me deeply. But please, allow me this one bit of selfishness."
No. 700672 bowed his head slightly.
"It’s not selfish at all," Jin said softly. He quickly pivotied to a different idea. "In that case, at least let me fix up the surroundings a bit."
Since Negadoll 001 had used the facility as a base, there were structural distortions and damage in several areas.
"Heh. Very well. I shall take you up on that kindness."
"It's settled then."
Jin immediately arranged for the transfer of an ether condenser identical to the one he had discovered underground.
Land brought the device in, and Reiko took it, placing it before No. 700672. It was roughly the size of a tissue box. Jin set it right by the ancient being’s bedside.
"What do you think?"
No. 700672 looked at the device, appearing genuinely surprised.
"This... where did you find this?"
Jin gave a brief explanation of how he had discovered it beneath his territory.
"I see... So my master’s descendants installed it, but the project was abandoned partway through..."
"That seems to be the case. However, as a side effect, a colony of giant centipedes appeared nearby."
"Hmm..." No. 700672 noted that free ether shouldn't cause gigantism in living creatures. "There must be another factor at play. Or perhaps that size was their natural potential, and they simply appear smaller elsewhere because they cannot grow to their full size."
"That makes sense."
According to No. 700672, a high-ether environment also extended the lifespan of biological organisms. The longevity of the demon race in this region was likely a result of both their Origin ancestry and the effects of the local ether.
Returning to the task at hand, Jin activated the Hourai Island-made ether condenser.
"Oh... this is quite pleasant."
The new model Jin had refined was far more efficient than the ancient version, drawing free ether from a much broader area.
"Magi Craft Meister... humanity truly does continue to evolve."
No. 700672 took several deep breaths, savoring the ether concentration that was now thick enough to be felt.
"Mmm... it reminds me of Hale. Jin-dono, you have my thanks."
Jin smiled. "Don't mention it. To borrow your own logic, I only did it 'for myself.'"
"Heh, I see. You've got me there."
The two shared a smile. Finally, Jin decided it was time to leave.
"Jin-dono, I am in your debt. Please, visit again. I am always available for consultation."
"Thank you. I'll be sure to do that."
With a promise to return, Jin stepped out of the "White Room."
In the days following, Jin gave orders to the Land squad and Smith squad to renovate the facilities around the "White Room" and install a Warp Gate. This ensured that No. 700672 would remain a vital advisor he could reach at any time.
And with that, the upheaval that had swept through the demon race finally came to a close.
"Ah, Onii-chan! Welcome back!"
Hanna greeted Jin the moment he arrived at Kaina Village after his three-day absence. Her missing front teeth had finally grown back, revealing a bright, even smile.
"I'm back, Hanna. Here, I brought souvenirs."
In the kitchen of the Martha residence, Jin set out cookies made from buckwheat—specifically, soba boro. He had made them by mixing buckwheat flour with sugar and eggs before baking them to a crisp. They were light and crunchy, with the subtle, earthy aroma of buckwheat.
Sara, the golem maid, brewed a fresh pot of tea. The cookies were the perfect accompaniment.
"These are so good, Onii-chan!"
"They really are delicious, Jin," Martha added.
"I'm glad you like them."
As he watched them eat, Jin thought it might be a good idea to start cultivating buckwheat in Kaina Village to make the cookies a local specialty.
High above the village, autumn clouds drifted lazily across the sky. In the surrounding fields, the stalks of wheat were beginning to shimmer with a golden hue.