A fine and important Japanese katana signed “Inoue Shinkai (井上真改)” and dated Enpō 7 (August 1679), bearing the Imperial chrysanthemum crest (kikumon) above the signature — a mark reserved for blades of the highest distinction.
Inoue Shinkai (井上真改) was one of the foremost Osaka-school smiths of the early Edo period. Active from around Kanbun (1661–1673) to Enpō (1673–1681), he succeeded his father Horikawa Kunihiro’s lineage through the Osaka tradition. His work was highly prized by the Tokugawa and Imperial families and later designated  Master Blades of Osaka Shintō. 
The blade measures 59.2 cm and exhibits a tight itame-hada with fine grain and clear nie-utsuri, together with a suguha mixed with slight ko-midare hamon of luminous clarity — typical of Shinkai’s mature Enpō-era style. The gold-covered copper habaki is of high quality, a technique rarely seen outside luxury commissions of the period.
The mountings include finely made fittings decorated with motifs of ducks and lobsters, crafted in rich gilt metal, reflecting the refined taste of upper-rank samurai patrons. The scabbard comes in a leather-cover, suggesting that it may have been carried onto the battlefield during the war.