— From the perspective of a Japanese sword polisher, what do you find difficult about sharpening kitchen knives? How does it differ from working on swords?

Even though both involve sharpening blades, the process for Japanese swords and kitchen knives is completely different—from the method itself to the shape of the whetstone and the sharpening angle.

For kitchen knives, you set a single angle and maintain it as you sharpen straight along the edge. Swords, on the other hand, have what’s called a hamaguri-ba—a clam-shaped edge. The area between the ridge line (shinogi) and the cutting edge is given a gentle, rounded curve, like the surface of a clam’s shell.

Knives are sharpened on flat whetstones, but swords require rounded stones. This is because swords need a sharply defined ridge line, and the polisher must carefully distinguish between the ridge, edge, and back of the blade so the angles don’t become rounded. A flat stone easily produces minute amounts of unevenness, and if sharpening continues in that state, the sword’s form can collapse, losing its graceful shape.

Because of these many differences, applying sword-polishing techniques directly to kitchen knives is quite difficult. It’s like saying both are “sports,” but one is football and the other is baseball—that’s how far apart they are.

 

— Regarding the shape of Japanese swords, have they always had the hamaguri-ba form?

Yes, the hamaguri-ba is a traditional shape. It’s a rational form designed to prevent chipping. Since swords are made to cut through hard objects, a thin, razor-sharp edge like that of a kitchen knife would chip easily. So instead, the edge is rounded and given more “meat,” sacrificing a little sharpness in exchange for strength.

The Japanese sword is often described with the expression, “cuts well, doesn’t break,” but in reality, it would be more accurate to say, “it doesn’t cut easily, but it doesn’t break”—its shape prioritizing durability. That said, there’s also a style called iai-togi, where the sharpening focuses on cutting performance above all else. The polisher removes some of the thickness near the edge, creating a slimmer line—it looks leaner, though you can still see traces of the hamaguri-ba curve.

I can’t say for sure how swords were polished in the distant past, but if you look at famous examples like Uesugi Kenshin’s treasured blade “Yamatorige,” you can see how full and rounded the surface is—it has a tangible sense of volume and thickness.

Ultimately, there’s no single “correct” shape. Some prefer a blade with more body, while others find a slimmer form more beautiful. Even among critics, opinions are divided. That diversity—that lack of a single answer—is what makes it so fascinating.

 

— As a polisher, what do you consider the true test of skill?

It all comes down to how beautifully you can bring out the hamon (temper line). For ordinary kitchen knives, practicality comes first—no one expects the hamon to be a work of art. But in swords, the hamon is essentially the star of the show. It draws the eye instantly.

A sword without a hamon feels lonely—almost pitiful. When a sword is burned in a fire, the hamon disappears; the entire blade becomes uniformly hardened, erasing the pattern. It’s not uncommon to polish an old, rusted sword only to find the hamon is gone.

In such cases, you might re-quench the blade to recreate the hamon, or use polishing techniques to make it appear as though a hamon still exists. It’s not deception—it’s an act of compassion, an effort to help the sword “look as beautiful as possible, even if just a little.” That’s how important the hamon is to a sword.

So I’d say the true measure of a polisher’s ability lies in how beautifully they can reveal the hamon and draw out its unique charm.

 

 

— When you polish, what is the most important thing you keep in mind?

The one thing I always remind myself is: “Don’t polish more than necessary.”

If it’s an old sword—something that has survived for decades or even centuries—it’s our responsibility to preserve it for future generations. Every time you polish a sword, the steel thins, and a little of its original form is lost. Over-polishing can destroy the sword’s true shape and spirit.

The same goes for modern blades. Carelessly grinding away a sword that a smith poured his heart into feels deeply disrespectful to the maker. That’s why, before I touch a sword, I always consider carefully: Which parts truly need polishing? Which should be left as is? How will the form change if I remove steel here?

Of course, making the sword look beautiful is important. It should inspire admiration at first sight. But if that “desire to beautify” takes precedence over preservation, the meaning of the work is lost. The goal isn’t to sacrifice the sword’s essence for the sake of appearance, but to bring out its beauty while keeping as much of its original form as possible. That’s what I strive for.

 

 

— For the “SOJA HOUCHO 真 –Shin–,” which you specially polished this time, what would you like overseas customers to experience?

I hope people can feel the value in a knife forged from tamahagane by a true Japanese swordsmith, and polished by a traditional sword polisher.

I’d like them to notice the subtle character of the steel—the faint grain (hada) and the softly emerging hamon—signs of the “sword-like spirit” that lives within this blade. Normally, when people pick up a kitchen knife, they don’t pay attention to those things. But with this knife, that attention to detail—the deliberate inclusion of swordlike qualities—is what makes it truly special.

Knives that simply “cut well” are easy to find. But this one carries a unique story: forged from tamahagane by a swordsmith, and finished by a polisher who usually restores samurai swords. That authenticity is where its real value lies.

If holding this knife sparks curiosity—makes someone think, “I’d like to see a real sword,” or “I want to learn more about Japanese swords”—then that would make me very happy. To have more people outside Japan discover this world, and maybe even say, “I want a sword for myself,”—that would be the greatest joy of all.