"That's it—a barrier!"
After nearly thirty minutes of deep thought, Jin finally looked up. He reached for the tea sitting in front of him and took a sip.
"Hmm?"
The tea was still at the perfect drinking temperature. Looking across the table, he saw Elsa smiling. Jin immediately understood.
"Elsa, have you been using Heat to keep my tea from getting cold?"
Elsa didn't answer, simply offering a gentle smile. Beside her, Reiko wore a similar expression.
"Thank you."
Jin finished the tea in one gulp and then requested a calculation from Laojun.
"Laojun, how long do you estimate the extra-large-class fragment will influence Ars?"
『Yes, My Lord. Assuming a speed of approximately 300 kilometers per second, I estimate its window of influence will be roughly 1,000 seconds.』
"I see. So that's the time it takes to enter within 300,000 kilometers—inside Uni's orbit—and then pass back out."
『That is correct.』
One thousand seconds was just under seventeen minutes.
"If we can maintain a powerful barrier for just thirty minutes to be safe, we might be able to minimize the impact."
"Jin-nii, what kind of impact are you expecting?" Elsa asked, having remained quiet until now.
"There might be a slight effect on gravity. Plus, smaller debris that has peeled off could rain down on Ars. Or perhaps Ars's atmosphere could even be stripped away by the fragment's passage..."
"None of those sound good," Elsa said, her brow furrowing.
"Yeah. To prevent that, I was wondering if we could project a barrier between us and the fragment."
"But wouldn't it have to be incredibly large to mean anything?"
"Exactly. I'd want it to be at least 100 kilometers in diameter. Ideally, around 1,000 kilometers."
Hearing the staggering figure of 1,000 kilometers, Elsa looked dumbfounded. "Wait, Uni has a diameter of 1,700 kilometers, so...!"
"Yeah, it's quite large."
"I think 'quite' is putting it mildly."
Elsa tried to imagine the amount of mana required to power such a barrier, but she couldn't even fathom the scale.
"Let's see... it would probably be equivalent to about 100 years' worth of ether consumption on Ars."
"That much!?"
"Yeah. That's just the nature of scaling up the size."
Jin kept his face neutral, but internally, he was also reeling at the consumption requirements. The difference in required mana between a 10-meter diameter barrier and a 1,000-kilometer diameter barrier was ten billion times—$10^{10}$. It was an astronomical gap.
"And Univasium is the key to managing that."
"How do you mean?"
Jin explained his plan to utilize the mana compression effect of Univasium. "It doesn't get much attention, but the 'compression effect' also includes aligning the phases of mana to increase efficiency. That's the part we need this time."
Elsa thought for a moment and then nodded. "Like a laser beam?"
"Exactly. Sunlight is incoherent light, whereas laser light is coherent. The efficiency is on a completely different level."
"I think I understand, more or less."
"It should reduce consumption by three to four orders of magnitude."
"That much!?"
"Yeah. However, the control is difficult. It looks like I'll have to rely on the golems again."
Still, a glimmer of hope had finally appeared.
"Four orders of magnitude is huge."
The difference between $10^{10}$ (ten billion) and $10^{6}$ (one million) was massive.
"I feel like we can manage something at that level."
"Mm, I agree."
Jin immediately used a piece of Univasium about the size of his pinky tip to craft a coherencer. "Let's see how this performs."
He promptly activated a barrier projector equipped with the coherencer.
"Oh?"
When he checked the device with Analyze, he found that even at minimum output, its strength exceeded the usual maximum.
"It's a success!"
"As expected of you, Father!"
"Jin-nii, that's amazing."
The coherencer allowed mana to pass through it before the magic was triggered. At that stage, the mana was aligned—made 'coherent'—and just like a laser beam, it produced a significantly greater effect. The output was approximately twenty times greater. Coincidentally, this was the same as the standard amplification rate of Elradrite.
"But it's still not enough..."
A factor of one million was still a long way off.
"...This is difficult."
"Truly."
Even Jin seemed to be reaching the limits of his brainstorming.
"In times like this, I think it helps to change your perspective," Elsa murmured.
Her comment reminded Jin of something. "I think someone once said that great ideas come to you when you're doing a handstand."
He paused, considering the thought. "A handstand... upside down... reversed... That's it!"
Jin's head snapped up.
"Jin-nii, did you think of something?"
"Yeah. A reversal of perspective. Instead of putting the barrier around Ars, we mount it on the Adriana and fly it between them."
"Eh?"
Jin explained that, essentially, the closer the shield was to the fragment, the smaller the barrier could be. "If we're at the midpoint, we could probably get away with 500 kilometers."
"Plus, it has the advantage of being mobile," Elsa added.
Jin nodded enthusiastically. "Right! Simply put, it's a shield. If we protect the areas most likely to be affected, we can make it work."
By the time the fragment approached Ars, the addition of the large force generators should be sufficient, and the Adriana likely wouldn't be needed for propulsion support anymore. When that time came, the Adriana could use this shield to protect the planet.
"That should give us a fighting chance."
They had finally found a path forward.
"Alright, let's start crafting."
The time was just past 6:00 PM.
"Jin-nii, after dinner."
"Eh? Oh, right."
Since every second wasn't yet a matter of life and death, Elsa prioritized Jin's health. Reiko felt the same. After eating a proper meal, Jin entered the workshop.
"Father, I will help."
"Me too."
"Yeah, I'm counting on you. Reiko, prepare the materials. Elsa, I'll have you handle these frames."
Thus, on Hourai Island, they continued to do everything they could, never stopping until the very end. There were only five days left until the fragment would pass near Ars.