Although an ancient document mentions that Yasutsuna from the border area between Izumo and Hoki who made 'Doji-giri' sword lived in the early 9th century, as seen in his existing work, it is widely believed that he didn't live in those days, but rather in the mid Heian period at the end of 10th century.
「童子切」の作者である雲伯国境の安綱は古伝書には時代を9世紀初めの大同年間（806年頃）とするが、現存作品を見る限りそこまで時代は上がらず、平安中期、10世紀末頃と見るのが刀剣史では通説となっている。