Tsunaie served as a retained smith of the Hojo house of Odawara in Sagami Province and is regarded, together with Tsunahiro, as among the more skilled makers of the late Soshu tradition. His period of activity is placed around the Tenbun era (1532-1555). Many of his works bear a five-character signature reading "Soshu-ju Tsunaie," though two- and three-character signatures are also encountered, the latter cut in bold strokes toward the mune side of the tang.

Tsunaie's workmanship is closely similar in style to that of Tsunahiro, and like his contemporary he specialized in fully tempered hitatsura. A representative wakizashi displays large gunome mixed with small notare, with tobiyaki, ashi, and ko-nie producing a vigorous hitatsura effect, while abundant chikei appear in a closely forged itame-hada with ji-nie and muneyaki. His tanto show a wide yakihaba with ko-notare mixed with gunome, the boshi turning in ko-maru with a long kaeri carrying yakisage that continues as muneyaki down to the base. The kitae across his productions is a dense itame-hada with well-adhering ji-nie. Tsunaie's horimono are likewise executed with considerable skill -- bonji, koshi-hi, rendai in layered carving, gomabashi carved kaki-nagashi -- adding a decorative dimension that complements the bold temperwork.

The NBTHK has designated both tanto and wakizashi by Tsunaie as fine works, with individual pieces judged a kasaku or kessaku among his extant productions. His surviving corpus, though modest in number, demonstrates a consistent command of the late Soshu idiom in forms ranging from compact hira-zukuri tanto with uchizori to sun-nobi wakizashi of wide mihaba and shallow sakizori.