The ground beside the great furnace at the riverside outpost was covered with gray-black blanks.
Gengorō crouched on the ground, holding the first kunai blank.
He turned it over and examined it several times.
Gengorō stood up and looked at the civilians helping nearby.
"Bring the whetstones. Sharpen a few first and try them out."
Shinichi stood nearby and watched.
Several civilians responsible for sharpening brought over whetstones.
They had been learning this craft from the artisans over the past few days, and now it came in useful.
They crouched on the ground one after another, picked up the gray-black kunai blanks, and began rubbing them against the whetstones.
The workshop filled with the rasp of grinding.
Before long, the first few blanks had been ground to bright, silvery edges.
Gengorō walked over and picked up a freshly sharpened kunai.
He scraped his rough thumb across its edge.
Then he walked over to a thick log nearby that served as a step.
Gengorō gripped the kunai and casually slashed downward.
There was a swish.
The kunai sliced smoothly into the wood, cutting off a large, thick strip.
The edge was sharp.
The strip of wood that fell to the ground had a perfectly smooth cut surface.
Several nearby artisans immediately gathered around.
They stared at the kunai in Gengorō's hand, then looked down at the piece of wood.
None of them had expected something produced in batches to be so sharp.
An apprentice felt the cut surface of the wood and could not help speaking up.
"Master, I really didn't expect this."
"Even without hammering them out bit by bit, kunai made in batches can actually have edges this sharp."
Gengorō did not respond to the apprentice.
Making a good kunai required more than a sharp edge; it also had to be tough enough.
It could not break when it struck another weapon in a fight.
Holding the kunai, he turned and walked over to the nearby anvil.
Gengorō raised his arm and struck the kunai hard against the edge of the anvil.
There was a sharp clang.
The kunai cracked straight through the middle.
The two broken pieces of iron fell to the ground.
Gengorō glanced at the broken pieces on the ground, then walked back.
He took several more kunai from the freshly sharpened pile and brought them over.
Standing before the anvil, Gengorō struck the kunai against it one after another.
Several sharp clangs rang out in succession.
Every one of those kunai cracked against the anvil.
The broken pieces of iron lay scattered around his feet.
The artisans nearby all fell silent.
The apprentice who had spoken earlier stared at the broken kunai on the ground and muttered quietly.
"Things made in batches really are brittle."
Gengorō did not ridicule Shinichi.
He turned and looked at the great stone furnace, over ten meters tall.
Then he looked back at the pile of black coal beside it.
Gengorō walked up to Shinichi.
"Lord Shinichi, this coal certainly burns fiercely."
"The furnaces in the Land of Iron could never produce a fire this hot."
He pointed at the broken kunai on the ground.
"The fact that the edges can be sharpened this well shows that the iron is excellent, and the fire is more than hot enough."
Gengorō continued.
"If we took these mass-produced blanks and hammered them out again..."
"We could definitely make ninja tools even better than those from the Land of Iron."
Shinichi could not understand why the kunai were so brittle.
He stepped forward, crouched down, and picked up half a broken kunai from the ground.
He activated his Tenseigan.
His pale blue eyes lit up as he looked down at the kunai's fractured surface.
Through the Tenseigan, he could see extremely tiny particles of impurities embedded inside the fracture.
Shinichi stood up and turned to look at the pile of coal beside the furnace.
His vision penetrated straight through the surface of the raw coal.
The same impurities were inside those lumps of raw coal.
Shinichi understood at once.
When the raw coal burned at high temperatures, it carried impurities into the molten iron.
Those impurities were precisely what made the mass-produced kunai so brittle.
Shinichi deactivated his Tenseigan.
He recalled some methods he had known in his previous life.
Raw coal could not be used directly to fuel a blast furnace for smelting iron.
First, the raw coal had to be placed in a pit and burned under cover to turn it into coke.
Only by using the coke to smelt iron afterward could they keep so many impurities out of the iron.
Shinichi called over several civilians working a short distance away.
He pointed to an open patch by the riverbank and told them to dig a large pit there.
The civilians took their tools and worked briskly.
Before long, they had dug a deep pit.
Shinichi told them to dump the entire pile of raw coal into it.
He had someone light the raw coal directly.
The fire soon blazed up.
Shinichi directed the civilians to cover the deep pit with layers of earth.
As they filled it in, they left only a few small vents at the top.
The whole pit of coal burned under the covering of earth.
The artisans stood nearby and watched.
One apprentice scratched his head and could not help asking a question.
"Lord Shinichi, why are we covering the coal with earth when it's burning so well?"
Shinichi did not answer, only telling them to look again in a few days.
A few days passed.
Following his instructions, the civilians dug away all the earth covering the pit.
The raw coal inside had changed completely.
It had turned into lumps of gray-black coke.
Shinichi walked up, bent down, and picked up a lump to heft in his hand.
It was lighter than the original raw coal and felt hard when squeezed.
The surface of the coke was covered with tiny, closely packed holes.
Shinichi activated his Tenseigan again.
He looked down at it.
Through the Tenseigan, he could see that the impurities inside the coke had indeed decreased considerably.
The civilians poured the coke and crushed iron ore into the great furnace.
Dozens of people took turns working the bellows, and the flames inside the furnace leaped ever higher.
The great furnace smelted another batch, and glowing red molten iron flowed out through the opening.
The molten iron ran along the stone channel and poured into rows of molds prepared in advance.
Once the molds had cooled completely and been knocked open, a large spread of gray-black blanks covered the ground.
Shinichi turned and called over Gengorō, who was standing to one side.
"Take the artisans and heat these mass-produced blanks until they're red-hot."
"Put them on the anvils and hammer them out again."
Without another word, Gengorō turned and led the apprentices and artisans over.
They picked up the blanks with iron tongs and placed them in the fire, then took them out once they were glowing red throughout.
More than a dozen artisans swung their large iron hammers and threw themselves into the work.
Dull hammering rang out all along the riverside.
They hammered repeatedly, tossing each finished piece straight into a nearby wooden bucket.
White steam rose from the water with a hiss as the blank was quenched.
These hammered blanks were then handed straight to the civilians on the other side.
Using whetstones, the civilians gradually sharpened edges along the blanks.
Then they carefully ground away the burrs on the surface and polished both sides until they shone.
Only after several days of continuous work was this batch of new kunai finally complete.
Hundreds of kunai gleaming with a cold light were laid out neatly on the ground.
Shinichi beckoned to several Hyuga ninja standing nearby.
"Go to the village storehouse and bring back some of the old kunai we made at our former clan grounds in the Land of Fire."
The Hyuga ninja ran off and soon returned carrying a wooden crate.
They set the crate down in the clearing, filled with old kunai that gleamed dully.
Shinichi grabbed several old kunai and tossed them directly beside the pile of new ones.
"Take a new one and an old one."
Shinichi pointed at the kunai on the ground.
"Strike them against each other. Put some strength into it and see which one breaks first."
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