Nagamitsu, the son of Mitsutada, is considered to have laid the foundation for the prosperity of the Osafune School of swordsmiths from Bizen Province (present-day southeastern Okayama Prefecture). In addition to tachi blades, he also produced halberds (J. naginata) and double-edged blades (J. ken). This blade with its brilliant tempering pattern is considered representative of Nagamitsu's work and is named Daihannya Nagamitsu, which comes from the association of its monetary value-six hundred kan in the Muromachi period (1392-1573)-with the six hundred volumes of the Great Perfection of Wisdom Sutra (J. Daihannyakyô).
This sword is said to have originally belonged to the Ashikaga Shoguns. Later it came into the possession of the warlord Oda Nobunaga (1534-1582), who gave it to Tokugawa Ieyasu (1542-1616) at the Battle of Anegawa in 1570. Ieyasu then presented it to his retainer Okudaira Nobumasa (1555-1615) in 1575 at the Battle of Nagashino.