After listening to Jin’s explanation for his visit, No. 700672 gave a solemn nod.
"So, it concerns the 'Failures.' And what, specifically, do you wish to know?"
"Ah, before we get to that, please have these."
Jin presented ten bottles of recovery medicine he had brought along, offering them to No. 700672.
"They are rich in ether."
Upon receiving them, No. 700672’s expression softened ever so slightly.
"Oh, this is the same medicine you gave me previously. I shall accept it with gratitude."
He immediately uncorked one and drained the contents.
"Hmm. As expected, it is remarkably effective. My thanks."
Watching her father, Neige stood by his side with a happy smile.
Once things had settled, Jin got straight to the point.
"A few days ago, one of the Failures utilized a technique called an 'Ether Stampede'."
"What? A blue-haired automata mentioned something of the sort recently. Could you tell me more about this Ether Stampede in detail?"
"Of course."
Jin proceeded to explain everything he currently knew regarding the phenomenon. No. 700672 fell into silence for a while, lost in thought. Once he seemed to have organized his ideas, he spoke slowly.
"An Ether Stampede, you say... That is a grave threat indeed. Neither I nor Neige would escape such a thing unscathed."
Neige reached out and tightly gripped No. 700672’s sleeve.
"It must be a weapon created by the Failures. I have no knowledge of it."
No. 700672 closed his eyes, contemplating the matter. Eventually, he opened them and looked directly at Jin.
"So, what you seek is a way to defend against it?"
"In essence, yes. To be more specific, I was wondering if you knew of any technology that can revert magic or mana back into ether."
"Hmm... In other words, you seek the technology to manipulate ether itself."
"I suppose that’s one way to put it."
No. 700672 lowered his gaze, falling into a pensive silence. When he finally looked up, his eyes were fixed on Reiko as he spoke.
"From what I can see, that automata there utilizes an ether converter and a mana driver."
It appeared No. 700672 could discern Reiko's internal power source at a glance.
"I can tell she operates with remarkable efficiency. However, my masters utilized 'magi reactors'."
"A magi reactor? Is that a device that converts ether into mana and simultaneously converts that mana into energy?"
"Precisely. You are quick to understand. That single device performs the functions of both an ether converter and a mana driver. Naturally, the energy loss is minimal."
Jin understood the logic perfectly; in fact, he had considered the concept before. However, he had abandoned the idea because the control was notoriously difficult and prone to overloading. He explained this reasoning to the homunculus.
"I see, so you have already considered it. The fact that it is prone to running wild is simply the flip side of precise control."
"I understand that much."
No. 700672 nodded once and continued.
"Now then, to answer your first question: to perfectly control ether, one would require '***'... Ah, I see. It does not exist in this world, does it?"
"I’m sorry, what was that?"
Jin asked him to repeat the word, as he hadn't quite caught it. No. 700672 nodded with a knowing look.
"***... Even the concept likely doesn't exist here. It was a common substance on Hale, the home planet of my masters. In your terms... shall we call it a 'mental catalyst'?"
"A mental catalyst...?"
Jin tried to vaguely envision what such a substance might be.
"You seem to understand how magic is activated, and you also recognize that mental waves are a type of mana wave. Well, if you use that substance, you can control ether with far greater efficiency."
However, there was no point in wishing for what didn't exist. Jin shifted his focus, knowing he had to work with the tools at hand.
"Well then, shall I share a bit of knowledge with you? Whether you can comprehend it or not depends on your own skill."
No. 700672 locked eyes with Jin as he began his explanation.
"All magic is triggered by mana."
Jin nodded silently.
"Then, what is the 'mana' we speak of? It is an invisible, powerful vibration."
This matched the hypothesis Jin’s group had formed. Jin nodded again.
"Because mana is a vibration, it possesses a wavelength, an amplitude, and a waveform."
No. 700672 looked at Jin's face, confirming his understanding before proceeding.
"It is this mana that gathers the ether existing in space, and it is mana that converts ether into mana. Furthermore, it is mana that converts mana into magic."
"Yes."
For the first time, Jin added a verbal confirmation as he nodded.
"Their roles differ, but all are a result of mana. Then, why is it that mana can perform so many different functions?"
No. 700672 peered into Jin's face as if testing him.
"Is it not due to the differences in wavelength, amplitude, and waveform you mentioned?"
At Jin's answer, No. 700672 nodded with satisfaction.
"Indeed. The most significant difference lies in the wavelength—or rather, the frequency. Now, all magi can emit a tiny amount of mana of their own. Let us call these mental waves."
"Right."
"Mental waves are the original mana a magi produces. By using these to convert surrounding ether into mana, and then converting that mana into energy, magic is manifested."
Jin sensed the direction No. 700672 was taking and concentrated even harder.
"As for the specific procedure for activation... you seem to know it already, so I shall skip that for now."
Up to this point, Jin had followed the logic perfectly. Looking at Jin, No. 700672 appeared a little impressed.
"Hmm. You have a sharp mind. Let us proceed further, then."
"Please."
No. 700672 gave a slight smirk.
"What is this energy? For fire-attribute magic, it is thermal energy. For wind-attribute magic, it is kinetic energy. Do you follow?"
Seeing Jin nod and sensing that he truly understood, a look of genuine pleasure spread across No. 700672's face.
"The mana known as mental energy is amplified into a greater mana, which then governs energy itself. That is an explanation of magic from a different perspective."
Jin felt the conversation was finally reaching the core of the issue.
"Depending on the attribute, the frequency of the mana used differs."
These were the exact words Jin had discussed with Saki on Hourai Island, now echoed by No. 700672.
"Now then, what kind of frequency do mental waves possess?"
Jin and his group hadn't been able to determine that yet. They lacked the means to quantify mana waves numerically.
Previously, at the Magi Craftman Guild in the Kingdom of Egerea, an automata named Dona had claimed to be able to read magic properties, but that was a different story. That was only a surface-level reading, not a true analysis of the magic.
To use an analogy, it was like the relationship between AM radio waves and the audio data they carry. The carrier waves have a frequency of about 530 kHz to 1600 kHz, and their amplitude and waveform represent the audio data. Since the frequency of audible sound is about 20 Hz to 20 kHz, the carrier wave has a frequency more than a thousand times higher. While the technical specifics of radio aren't necessary here, audio signals are extracted from radio broadcast waves through a process called demodulation.
In this context, the magic that ordinary people can perceive is equivalent to that audio signal. The carrier wave's frequency is simply too high for the average person to detect.
That was exactly what No. 700672 was explaining.
"Among all forms of mana, mental waves possess an exceptionally high frequency."
This was new information for Jin. He listened intently, his eyes sparkling with curiosity. Seeing his reaction, No. 700672 asked a question in a challenging tone.
"Regarding your automata, what attribute of magi-crystal are you using for her ether converter?"
"An all-attribute one."
Hearing that, No. 700672 shook his head.
"As I thought. That is a trap that many easily fall into."
"Why?"
Reiko, who had been silent until now, couldn't keep quiet after hearing her master’s work being questioned. Her sudden intensity made Neige, who was standing by No. 700672, glare at her in return.
"Reiko, it's fine....I see. You're saying I should use a light-attribute or dark-attribute magi-crystal, right?"
Upon hearing that, No. 700672 gave a deep, satisfied nod.
"Precisely. Since the frequency is high, it might seem like the dark attribute would be appropriate, but it is known through experience that light-attribute magi-crystals are the most efficient."
While an all-attribute crystal does contain the light attribute, it contains all other attributes as well. Because they are all present simultaneously, the efficiency for this specific purpose is diminished.
"This is strictly regarding the ether converter. For the actual exercise of magic, an all-attribute crystal is still quite effective in its own way."
"That makes sense."
For Jin, this was becoming a gold mine of information.
"Now, regarding the power to manipulate ether, I believe you have grasped a great deal from our talk thus far."
"Yes, certainly."
Jin nodded immediately.
"Now, how to control that mana? Naturally, the foundation is mental energy. One cannot do anything that exceeds the upper limit of their own frequency. As for you... how do you measure up?"
"I couldn't say. Currently, I have no way to measure the frequency of my mana waves."
"Hmm, you are honest....Neige, guide him."
"Yes, Father."
That brief exchange was enough for Neige to understand. She took Jin’s hand and led him over to one of the "windows" set into the wall.
"Emit your mana toward that 'window.' You can tell roughly where you stand by the color it produces."
"Understood."
Jin concentrated his mana into his palm and released it toward the window.
"Oh!"
No. 700672's voice was tinged with surprise. Jin, however, didn't yet understand the significance.
"This is...?"
The previously dark window was now glowing with a brilliant, vibrant blue light.