Historical records show that Priest Masamune was the most well known blade smith ever lived in Japan. Even though he lived in the late 13th and the early 14th centuries, the sword collections of the Tokugawa shogunate in the 18th century used mostly his swords or the swords made by his students. He introduced the “nie” method of using martensitic cyrstals and the style of undulating temper line. According to a legend, he was challeneged by Muramasa who was also a very famous blade maker of his time. When they held their swords in the river, for a moment they saw that Muramasa’s sword cut everything in its way perfectly, the fish, the leaves and even the air blowing above the water while Masamune’s blade only cut the leaves. Muramasa declared he was the winner. A monk who was watching them yelled: Masamune’s blade is the best, it does not cut the innocent.