In the doctor's later years, he visited the spring of Yunohana to treat his rheumatism. He also knew that the country was home to many skilled smiths, and worked with them to create a rifle of incredible force and precision. The gun was named for the doctor, as read in the traditional language of the land of hot springs.
Tanegashima was a type of matchlock or arquebus firearm introduced to Japan through the Portuguese in 1543. Tanegashima were used by the samurai class and their foot soldiers (ashigaru) and within a few years the introduction of the tanegashima in battle changed the way war was fought in Japan forever.