After a slightly early dinner, Jin leaned back on the sofa, lost in thought as he reflected on the day’s events.
"Jin-nii?"
Seeing him like that, Elsa seemed to sense his mood. Thinking it best to leave him to his musings, she kept a respectful distance.
"Wedges... pickaxes... drills..."
He was muttering to himself in a way that might have seemed a bit strange to an outsider, but Elsa had long since grown accustomed to this being Jin’s way of thinking.
About five minutes later, he suddenly snapped out of it.
"Alright, the concept is set. Now I just need to ask a few questions."
Jin stood up energetically. "I’m going over to see Mii for a bit," he announced before heading for the door. The move was so sudden that only Reiko managed to follow him immediately, while Elsa could only manage a small "Mm" in response.
＊ ＊ ＊
Jin returned about thirty minutes later, his face beaming with satisfaction.
"Did something good happen?" Elsa asked, unable to ignore his expression.
"Yeah, it did. You remember that massive boulder that was causing trouble at the construction site today?"
"Mm."
"Reiko crushed it for them then, but I went back to ask what they usually do when that happens."
"I see."
"Duza-san, the site supervisor from earlier, is staying here too, so I was able to talk to him."
Since there were no suitable lodgings near the construction site, Duza was staying in the staff quarters.
"Is that so?"
Elsa had seen the look of intense interest on Jin's face earlier and figured something had struck a chord with him. She just hadn't expected it to be civil engineering.
"Anyway, he said that when they need to break rocks, they just tap away at them with hammers and chisels."
"...Are you planning to do something about that?" Elsa asked. She could already tell the answer by the look in his eyes, but she asked for confirmation anyway.
"Yeah. I’d like to be of at least a little help."
With that, Jin made a quick trip back to Hourai Island.
"It should work well enough if I use adamantite for the high-impact parts," Jin mused.
"Father, what will you use for the rest of the body?" Reiko asked.
"Carbon steel... no, let's go with nickel steel."
"Understood."
With Reiko’s assistance, Jin crafted a pickaxe. The tip was tipped with adamantite, making it capable of biting into almost any rock. He also applied Toughening to the nickel steel body, ensuring it had more than enough structural integrity.
"I'll make some chisels as well."
These also featured adamantite tips. Jin estimated they would allow for roughly three times the excavation speed of standard tools.
"And finally... this."
"Is that a drill?"
"Right. I remember hearing that one way to split rocks is to drill holes and then drive wedges into them."
"I see."
What Jin was making was a hand-operated drill—specifically, a type known as a brace. Because the design relied on a simple crank handle, it was unlikely to break even under heavy use. Naturally, the tip of the drill bit was fashioned from adamantite.
After producing ten sets of each tool, Jin returned to Mitsuho.
＊ ＊ ＊
"Welcome back."
When Jin arrived back in Mitsuho, it was 8:30 PM. He had Reiko carry the samples and headed straight for Duza’s quarters.
"Jin, what have you got there?"
He ran into Reinhard and Mii in the hallway. It seemed they had been finalizing the schedule for the following day.
"Jin, what is that?" Reinhard asked, his keen eyes immediately fixating on the tools Reiko was carrying.
"Tools for the construction project. This is a pickaxe, this is a chisel, and this is a drill."
"Hmm. That drill has a fascinating shape!"
"I’m on my way to see Duza-san now."
"In that case, I’m coming too!" Reinhard replied. It was exactly the kind of response Jin had expected.
Jin knocked on the door to Duza's room in the staff quarters. "Duza-san, are you in?"
"Oh, Jin-sama! Is there something else you needed?"
"I’ve prepared something you might find useful. Please, take a look."
In the staff quarters' break room, Jin laid out the tools Reiko had been carrying.
"Ho, these look interesting!"
"They are a chisel, a pickaxe, and a drill," Jin explained briefly.
"I understand the chisel, but what about this one?"
"This is used like this."
Jin demonstrated the proper way to handle the pickaxe. It was a simple matter of a full-body swing, but the balance was perfect.
"Aha, I see! This is excellent. It looks like it could dig through stony ground with incredible efficiency."
Being a man with years of field experience, Duza immediately recognized the utility of the pickaxe.
"And this is the drill."
"A drill?"
"Yes. Um, is there anything around here that I could try boring a hole into?"
Mii thought for a moment before heading to the kitchen. She returned a moment later carrying a large ceramic jar.
"How about this? The rim is chipped, so I was thinking of turning it into a planter anyway."
"In that case, it’s a perfect test subject."
Ceramics were quite hard and notoriously brittle; drilling a hole into such material usually required specialized equipment and a great deal of skill to avoid shattering the piece.
Jin flipped the jar over so the base faced upward. He placed the adamantite tip of the drill against the center and began to turn the crank.
"Oh!"
The adamantite bit ground through the pottery as if it were nothing, boring a clean hole in seconds.
"T-This is incredible! As expected of Jin-sama!"
"J-Jin-sama, are you really going to let us have these?" Duza was so delighted he practically jumped for joy, and Mii’s eyes were sparkling with equal excitement.
"Yes, that's the plan."
"We are truly grateful!"
From there, Mii and Jin began to discuss the terms of the trade.
"As far as I'm concerned, these are a token of friendship, so a minimum price is fine," Jin offered.
"We couldn't possibly accept that," Mii insisted.
"But..."
After a brief back-and-forth, they reached a compromise. In addition to the miso and alum he was already set to receive in exchange for the ladder climber design, they would increase the quantities of both. Furthermore, they agreed to provide him with paulownia wood—a resource he had noticed in the workshop that wasn't available on Hourai Island.