Satisfied with their provisional success, Jin and the others began considering the prototype for Unit 3.
"I still feel like the projected image from ten meters away is a bit too large," Jin remarked.
To which Eira suggested, "Hey, why don't we make the casing telescoping?"
"That's it!"
Since the pinhole method didn't require manual focusing, he hadn't felt the need for such a mechanism, but having that function would definitely be useful for their experiments.
Man, to only realize that when prototyping Unit 3...
I shouldn't let preconceptions blind me, Jin secretly reflected.
Before long, Unit 3 was completed.
Thanks to the added telescoping mechanism—that is, the ability to change the focal length—they were able to determine the optimal size for a magic circle projected from ten meters away.
"That worked out well. The whole thing got a bit long and slender, though..."
Increasing the focal length inherently meant increasing the overall length of the device.
Modern telephoto lenses in Japan used combinations of multiple lens elements to keep the overall length short, but until fairly recently, a telephoto lens was simply assumed to be long.
Setting that aside, now that they had achieved initial success, the next step was to improve its performance.
"Hey, what would happen if we halved the overall size?" Eira proposed.
"If we did that, the projected image would probably be halved too," Jin replied.
Encouraged by his response, Eira pressed on with enthusiasm.
"It seems like we could make the whole thing much more compact, but what do you think?"
"The projection data would become that much smaller too, which means we wouldn't be able to draw complex magic circles."
"Ah, right."
At Jin's point, Eira's shoulders slumped.
"However, if we have a small golem draw them for us..." Jin immediately offered a solution.
"Ah, of course!"
"I see, so they can be used like that too," Groma noted, catching on as well.
"In that case, we might even be able to shrink it down to a quarter."
"But if we do that, the projection distance will likely be reduced to a quarter as well, so wouldn't we need to come up with a way to extend it?" Kachea advised.
"That's true. Which means we'd need an even stronger light source than what we have now... No, wait."
Jin realized that the light source itself didn't need to be shrunk to a quarter.
While that would make the light source portion relatively large in proportion, it wouldn't look terribly unrefined.
"And if we use high-quality light-attribute magi-crystals, we should be able to downsize it a bit more, too."
Incorporating these ideas, they decided to prototype the fourth generation... Unit 4.
They decided to keep the reduction to one-half rather than one-quarter.
At that size, they would still be able to create the projection data themselves.
"That should do it."
It was completed at 4:30 p.m.
Renting the Grand Conference Room once again, their experiment proved successful, leaving Jin and the other three thoroughly satisfied for the day.
"Let's wrap it up here for today....Thank you very much as well, Jin-dono."
"Good work today."
The early wrap-up was because the analysis results of that information crystal were scheduled to be presented later that evening.
Because of that, everyone was going to have an early dinner and stand by.
Jin returned to his guest room for the time being to join Elsa.
After refreshing himself in the room's bath, he had room service for dinner at 5:30 p.m.
"...Did you do anything interesting?" Elsa asked while sipping her post-meal tea.
"Yeah. We made this and that..." Jin explained the magic circle projection technology.
"Interesting."
"Right? Doing your best within these kinds of constraints is really rewarding."
Looking back, when he had been hurled into this era all by himself without any support from Hourai Island, he had completed Hope using only whatever materials were on hand. The sense of accomplishment back then had been tremendous.
Jin reminisced about that time.
"It's something I need to remind myself of again and again. 'Never forget your original intent,' as they say."
"Nn, I understand the feeling....Now, my turn."
Elsa likewise reported the day's events to Jin.
"I see, so Najas is doing well too."
"Nn. From what I casually heard, she's already caught up with everyone."
"Is that so?"
Since her enrollment had been something like a mid-term transfer, he had been worried about whether she could keep up, but Elsa's education had clearly hit the mark.
"Nn. Everyone listened enthusiastically. I'm looking forward to the future."
"That's wonderful."
Jin hoped that, this time around, he could support the future development of this world from the shadows.
Just then, it grew lively outside the window. The time was 6:00 p.m.
For a moment, Jin wondered what was happening, but...
"Ah, Deus Ex Machina must be back," he quickly deduced.
He then decided to inquire with Laojun through Reiko.
"Reiko, there weren't any issues, right?"
"Yes, Father. It seems everyone enjoyed themselves."
"Then all is well."
Jin decided that he could simply hear the details after returning to Hourai Island.
Thirty minutes later, there came a knock at the guest room door. Hope answered it.
"The reporting session for the information crystal's analysis results is about to begin. Will you be attending?"
The one asking was Fione Fias.
It seemed she had returned to her secretarial duties right after getting back. It was very like her earnest nature.
"Yes, please lead the way," Elsa answered.
Jin, of course, was just as eager to hear it, just as he had told Manon earlier that day.
"Please come this way, then," Fione Fias said, guiding them toward the auditorium.
Half the seats in the auditorium were already filled.
"Jin-sama, Elsa-sama, this way, please."
Jin and Elsa were guided to special seats in the very front row facing the stage.
"Please wait about ten more minutes," Fione Fias informed them before stepping away.
"Looking forward to it."
"Yeah, me too."
Jin and Elsa eagerly awaited the moment the report would begin.