Nagamitsu (active in the late Kamakura period) was the son of Mitsutada, the founder of the Osafune School of Bizen Province (present-day southeastern Okayama Prefecture). Nagamitsu is said to have laid the foundation for the prosperity of the Osafune swordsmiths. In addition to tachi blades, he also produced halberds (J. naginata) and double-edged blades (J. ken). He successfully continued Mitsutada's style, creating bright, flamboyant clove-shaped (J. chôjiba) tempering patterns on beautiful metal finishes. This excellent piece was passed down within the Ikeda family of Inaba Province (present-day Tottori Prefecture).