Master Blacksmith in Demon Slayer

But he suppressed this surge of excitement and decided to first pay respects to his own stomach.

Yesterday's lesson had made it abundantly clear that the human body has limits—without replenishing enough energy, it simply wouldn't work.

He immediately went back to prepare breakfast, ate his fill, then returned to the anvil, adjusted the Fireman Mask on his face, and lit the forge.

The scale marks on the iron ingot were no different from yesterday, but the metal, now fully cooled, gave off an extraordinary impression.

As the forge temperature rose, the ingot gradually glowed red and grew soft.

Locking onto the current mark, Tetsu no Sosuke took it out and placed it on the anvil.

"Purging impurities and forging iron into shape are not the same. What I need to do now is form the shape of a blade. Its length, thickness, and overall form will all change under the continuous strikes of the Forging Hammer. The weapon's toughness will also be decided in this forging process! This is the true critical moment!"

Clamping it with tongs, Tetsu no Sosuke didn't hesitate for a moment. A single hammer fell. Ding!

Sparks flew, and at the same time, a sound reached his ears.

[Toughness +1]

"Just as I thought!"

He mused inwardly, but the Forging Hammer never stopped falling.

The prompt [Toughness +1] kept coming to his ears.

Amid these prompts, the iron block in his hands slowly stretched and elongated from a square shape, faintly taking on the form of a blade.

But just then, the prompt changed.

[Toughness -1]

[Hardness +1]

"...Huh?"

This prompt made Tetsu no Sosuke pause slightly: "So, the first stage is removing impurities, the second is accumulating toughness? The third stage grants other attributes, but while granting them, it constantly wears down toughness?"

A guess formed in his mind, and he ignored the prompts, hammering and refining the iron repeatedly according to the method he remembered.

This step was faster than the previous one.

By around noon, the blade body had basically taken shape.

At the same time, he had summarized several attributes.

Toughness, hardness, impact resistance, and abrasion resistance—four in total.

Consistent with his initial summary, after the first step of impurity removal, the second was accumulating toughness. Every hammer strike during this phase increased toughness.

But just as the blade's form was nearly complete, toughness began to be steadily consumed.

In its place, the other three attributes grew.

After a morning of forging, Tetsu no Sosuke discovered that different hammering techniques yielded different results.

In short, if he used only one specific hammering method, the blade would continuously enhance that particular attribute—say, hardness—but the consumption of toughness remained constant.

Worth noting, quenching also boosted several attributes, even improving toughness.

"So, forging a blade ultimately comes down to finding a balance among these four attributes?"

He looked at the nearly finished blade in his hands, thoughts swirling in his eyes. Seizing the right heat, he landed the final few strikes, completing the entire blade-shaping process.

Then, Tetsu no Sosuke carefully placed the blade into the forge.

"Heat the blade to the proper temperature, then take it out to cool naturally. After that comes the sharpening of the edge."

Tetsu no Sosuke's expression was intensely focused. Even with the progress bar's help, he dared not be careless.

How a blade ultimately performed depended entirely on the swordsmith's dedication and technique during the forging process.

Every step now determined the blade's future.

"Though you're destined never to become a Nichirin Blade—after all, you're made from ordinary iron ingots—to me, you are the first sword I've ever forged. That means everything!"

Chapter 4: Breath of the Sun

Sunlight spilled across the mountain stream. On one side, the forest buzzed with insects and birdsong; the babbling of the brook was a balm to the soul.

Tetsu no Sosuke was now sharpening the blade.

The entire annealing process had taken a full day.

During that time, aside from waiting, Tetsu no Sosuke had crafted the other parts of the sword.

The tsuba, the hilt, and so on...

Now, before the whetstone, Tetsu no Sosuke endured both pain and joy.

Sharpening the edge was a focused, repetitive process. The annealed blade was very soft, and one slip could ruin everything.

So the process demanded intense concentration.

And the constant grinding was a cycle of repetition. Combined, the swordsmith's ordeal was no less than that of the blade being honed.

That was the painful part... as for the joy—

[Sharpness +1]

[Constitution +1]

[Sharpness +1]

[Strength +1]

Unlike the earlier shaping, each stroke of the whetstone now added a sliver of sharpness to the blade. And, to himself, a random point of attribute.

Just listening to these sounds, Tetsu no Sosuke felt as if he were hearing celestial music. In comparison, neither the murmuring Water Stream of messages beside him nor the birdsong and floral fragrance of the forest could replace it.

The only pity was that such focused, meticulous, error-free polishing could not last long.

Soon, the blade edge was finished.

The next steps returned to heating, quenching, and increasing hardness. Once all that was ready, one or several rounds of tempering followed.

During this process, Tetsu no Sosuke wrapped every part of the blade except the edge in clay, then sent it into the furnace.