Naoyasu was active as a swordsmith in Yanagawa during 19th century after studying on how to forge swords under Soji Naotane in Okachimachi, Edo.
In the history of Japanese swords, the production of swords before 1596 are called ‘Koto (old sword)’, and were distinguished from ‘Shinto (new sword)’, made after that.
In the Shinto era, each feudal clan began to hire expert swordsmiths from every part of the country. Due to this change, swordsmiths started to move actively from their hometowns. As a result, sword style of each province was then found in various areas in Japan.
This sword was made in Yanagawa (Fukuoka Prefecture), but it shows Sōshu den style (Kanagawa Prefecture).