Such was the advance in swordmaking that Masamune brought to the samurai soul. In Japanese folklore, his swords are often contrasted with a later distinguished master, Muramasa. A mythical comparison of their blades, demonstrated how Masamune had achieved the pinnacle of his craft.
‘To test the swords, each sword was held into the current of a
stream. Muramasa's sword was said to have cut a leaf in half
that simply touched the blade from the current alone. But the
master Masamune's sword did not cut a thing, with the leaves
miraculously avoiding it at the last second, as if to show it
possessed a benevolent power that would not harm anything that
was innocent or undeserving - even a simple leaf...’
Masamune’s swords, considered deeply spiritual, pure and benevolent, had devolved into Muramasa's brutish evil steel violence.
Part of what had caused this loss of Golden Age metallurgical skill was the fierce demand for ferocious utilitarian disposable weapons to be churned out quickly in the 100 year Sengoku civil war. During the later Muromachi period, more than 200,000 nihontō were shipped to Ming Dynasty China in an official trade attempt to soak up the production of Japanese weapons and make it harder for local pirates to weaponize; the other part was the arrival of the gun, in 1543, which turned swordsmiths into gunsmiths. Form follows function.
Once the country was united by Shogun Hideyoshi, the peasantry was disarmed, and in the 400 years of peace that followed, the gun was rejected and the sword of the samurai was elevated to a fine art, although never to the same level as those made by Masumune.
These more ceremonial blades were known as shinto ‘new swords,’ and often more ornate and decorative than practical. In 1876, when the Samurai were officially disbanded, all civilians were ordered to give up carrying weapons.