The next day, the 6th.
The fireworks were scheduled to be launched that night.
The town was even more bustling than the day before.
Chidoritei, too, appeared to be almost completely full.
"I wonder if this event is fairly well known."
With the arrival of the new day, another question had occurred to Jin.
"Are there really no other towns that launch fireworks?"
"...Indeed."
Though he didn't know where the fireworks came from, Jin remarked that there was no real reason for them to be set off exclusively in a frontier town.
"Are fireworks that expensive? Or is the manufacturing method so specialized that they can't be made elsewhere?"
He floated a few guesses, but came up with no answers.
"Does Laojun have any leads on this?"
When he asked Reiko, she gave an affirmative nod.
"I can explain it to you, but what would you prefer to do?"
"Let me see..."
Demanding immediate answers every single time took the fun out of things, depending on the situation.
"This time, I think I'll look and listen around a bit myself before asking."
After all, this was a little getaway, and they had come here to enjoy themselves, Jin noted as he glanced at Elsa.
"Nn, thank you."
Elsa was thoroughly enjoying the trip as well, so she readily agreed.
"Alright then, let's go ask around a bit."
Jin and Elsa decided to steer clear of obvious tourists and focused instead on questioning people who looked like locals.
"...Well, that was a bust."
"Nn, no luck."
Their inquiries had ended in vain; not a single person knew the reason.
Everyone's attitude was simply that more tourists were visiting thanks to the fireworks, so what was there to complain about?
Well, to be precise, there was just one person who gave a different reply:
"I'd like to know that myself, but I haven't the faintest clue."
That person had gone on to say:
"The fireworks are launched in the neighboring country, so building a business that leeches off their display could fall apart at any moment. Failing to plan for what to do if that happens is the height of foolishness."
The speaker had been the proprietor of a magi-device shop facing the main street.
"All I can say is, I hear 'the manufacturing method for fireworks is a closely guarded secret, not something anyone can whip up just like that.'"
"Is that so?"
Leaving the magi-device shop behind, Jin mulled over the man's words.
"Not something anyone can whip up, huh..."
True enough, traditional fireworks required gunpowder, and that gunpowder was made by blending saltpeter, sulfur, and various other combustible materials and colorants.
However, the fireworks Jin and Saki had developed in the past were different. A substantial portion of the chemistry had been replaced with magical materials.
"...In other words, the technique for making so-called 'magical fireworks' has been lost to time."
That meant the only craft remaining was traditional gunpowder fireworks—originating from Mitsuho, whether one could truly consider that the original method or not.
"I see. Maybe they launch them out here on the frontier rather than in the middle of a town precisely because they use gunpowder."
At this point, Jin decided it was time to let Laojun fill in the blanks through Reiko.
"Father, your deductions up to this point are almost entirely accurate. Since you are unlikely to find further details in this town alone, allow me to explain."
"Yeah, please do."
"A fireworks artisan used to live on the outskirts of the town of Naize, just across the border in the Klein Kingdom. He was the sole fireworks artisan in the Allied Kingdoms."
"Oh, really?"
"Yes. Fearing an accidental gunpowder explosion, he chose to live in such a remote frontier region. Furthermore, 'saltpeter' could be harvested in the nearby mountains."
Saltpeter referred to potassium nitrate, KNO3.
It was a type of nitrogen compound. When organic matter in the soil or urea from animal waste broke down into nitrogen compounds, bacteria oxidized them during decomposition, forming salts with potassium ions... or so the theory went.
Because it was water-soluble, rainfall caused it to leach deep into the ground. In addition, potassium nitrate was readily absorbed as nourishment by plant roots, making it difficult to harvest naturally in regions with high rainfall.
For that reason, back in Japan, saltpeter had historically been manufactured by fermenting and aging night soil.
"Saltpeter, huh. That really is rare in this world..."
Within the scope of Jin's knowledge—or rather, according to Laojun's surveys—the places where natural saltpeter could be gathered were extremely limited.
Most deposits were found deep inside caves, suggesting they originated from the guano of cave-dwelling creatures like bats.
As for explosives, Hourai Island possessed blasting charges based on "mana bomb," meaning that volatile, hazardous gunpowder was only ever kept around as a laboratory reagent.
However, creating vivid, blossoming flowers of color across the night sky was difficult with "mana bomb" alone.
"Reiko, you spoke in the past tense just now. Does that mean...?"
"Yes, Father. That artisan lived roughly 170 years ago."
"In that case, there must be 'someone' carrying on the trade today."
"Yes, Father."
"Hmm... That piques my curiosity. I intended to just travel through the Kingdom of Franz, but now I really want to know who's setting off these fireworks."
"Nn, I understand."
Elsa nodded in agreement, clearly just as intrigued. That meant even she didn't know the finer details.
Assuming that Laojun already knew the whole truth, Jin eagerly looked forward to nightfall.
At last, the long-awaited night arrived.
Around eight o'clock in the evening, a giant flower of light blossomed in the eastern sky.
"Oh, that's definitely a firework."
It was not quite as dazzling as the displays seen in modern Japan, but rather a simple, rustic firework of old.
They were being launched at a steady pace of about one shell per minute.
Gasps of delight and cheers from tourists erupted all around the town.
It was certainly a breathtaking sight against the pitch-black night sky. Jin could easily see why people flocked here in droves.
"I wonder how many shots they'll fire."
"Ah, the color changed."
"You're right."
Starting with the third shot, the whitish glow shifted toward a reddish hue, turning green by the fifth. From the seventh burst onward, the sparks flared blue, before returning to white for the tenth.
With that, the display came to a quiet end. It had been a fleeting phantasmagoria of about ten minutes.
"If they launch more tomorrow, we should be able to pinpoint the exact location."
"I think Laojun has already pinpointed it, though."
"Well, that's true....Which means we ought to be able to find out who's launching them, too."
"Nn."
Jin considered the logistics. Hiking out there in person would be tricky.
There was every chance the launch site was tucked deep away in the mountains.
"Guess I'll just ask Laojun after all."
"I think that's best."
"Alright."
Jin reached out to Laojun through his Fellowship Bracelet.
"Laojun, do you know who is launching those fireworks, where they're doing it, and why?"
"Yes, I have all the details. Shall I brief you?"
"Yeah, please."
"Understood."
With that, Laojun began his explanation...