Samurai Sword - Linked | Explorer

NARRATOR: See this? This is a samurai, an elite Japanese warrior. And this is his sword, his samurai sword. Watch out! It's super sharp. They've been around for over 1,000 years, as iconic to Japanese culture as cherry trees or Mt. Fuji.

And thanks to, of all things, a blacksmith, a potter, and an ancient scroll, you can still buy a totally 100% custom-made katana blade today. Seriously awesome. So, random question-- how exactly is this ancient knowledge of making iconic Japanese samurai swords still around?

Well, it's a pretty incredible story of ancient scrolls, fiery forges, and the most expensive steel on the planet. Let's take a deeper look at how the sword and the scroll are linked. The Shimane Prefecture in Japan is wild with plunging cliffs and volcanic islands. It's full of sacred Shinto shrines and waterfalls, believed to bring victory to bullfighters and sumo wrestlers who drink its waters.

And sometimes, its rivers run red, blood red. But not with blood. That's disgusting. With iron deposits. And that's how the blacksmith made a living in this region. He smelted that iron into steel until he and his buddy, the potter, found an ancient scroll. That taught them how to make-- drum roll please-- [drum roll] --samurai swords. Total job upgrade.

Nowadays, there are only about 200 traditional swordsmiths left in Japan. Shunji Kobayashi is one of them, thanks to his grandfather, the blacksmith. So why is his craft disappearing? Never mind that society and warfare have totally changed. Making real swords is a long process, and they'll cost you upwards of $25,000 a pop.

But remember those iron deposits? That iron sand is put into a tatara, or a clay tub furnace. This is the only one left in Japan. It's heated, mixed with charcoal to add carbon, and voila! Steel. Tamahagane steel, the most expensive steel in the world.

And that curved shape comes from layering two kinds of steel and submerging that red hot, fresh from the forge sword directly into the water. Contracting metals bend inward to form that lethal, legendary blade. And when you're holding one, you're holding a millennium's worth of trade secrets. No pressure there, Shunji.

Shunji Kobayashi says it takes six months just to make one sword, and it takes five years of training just to polish a katana properly. The whole swordsmithing thing requires patience and attention to detail, much like the samurai themselves, which is why the katana is known as the soul of the samurai.

But that's not the whole story. For more on the sword and the scroll, watch "Explorer" on National Geographic.