Tosa-jū Yasumitsu (土佐住安光), was a provincial smith working in Tosa Province during the early to mid Edo period (17th century). Blades from Tosa are generally practical in nature, forged for actual use rather than display, and are known for their straightforward construction.
This sword has a nagasa of 63.6 cm. The hamon is distinctive, showing two pronounced undulations near the base, transitioning into a straight suguha toward the tip, a feature sometimes seen in regional work emphasizing strength at the machi.
The blade is mounted in an early Type 98 Army officer koshirae with an iron scabbard, a configuration associated with the early years of the Pacific War. The combination reflects the common wartime practice of mounting traditionally forged blades for military service.