Tsunahiro (綱広) was a leading smith among the Sue-Sōshū group who brought the forging tradition to its final flourishing in the late period. The first generation is said to have been a descendant of Hiromasa, initially succeeding to that lineage name before being summoned by Hōjō Ujitsuna to Odawara, where he received the character (綱) and changed his name accordingly. His earliest extant dated works bear Tenbun-era inscriptions, establishing him as the , and the lineage continued in an unbroken succession — the second generation in Tenshō, the third in Keichō, the fourth in 'ei, and the fifth around Manji — with smiths using the name persisting even into the Meiji period. As a highly skilled maker in the line following Hiromitsu and Akihiro, Tsunahiro stands out as a craftsman who most faithfully preserved the Sōshū-den style during this late period.
Tsunahiro's works characteristically display mixed with , with the grain standing and showing and . His signature is a incorporating , -shaped elements, and , with and entering throughout. The hallmark of his oeuvre is the — a full-temper effect achieved through conspicuous and that spread across the blade surface, sometimes forming crescent-shaped islands of tempered steel. In his best work, adheres well and and run through the temper, while the tends to be tight. His are typically with , wide , and extended , while his overwhelmingly favor construction with wide proportions and pronounced . It is also recorded that the third-generation Tsunahiro was summoned by Tamenobu, lord of Tsugaru Castle in Ōshū, to forge swords in that domain — blades known as "Tsugaru-uchi," some bearing the inscription "within three hundred ," constituting important historical documentary material. are frequently encountered on Tsunahiro blades, including grass-style , with , , and incised devotional and literary inscriptions, all executed with considerable skill.
Tsunahiro occupies a position of singular importance as the foremost representative of the final phase of the tradition. His output was large and many works survive today, ranging from pieces — unusual for the school but occasionally encountered — to the vigorous compositions for which he is best known. Both the and of his finest blades show abundant formation, and among his extant works certain pieces are regarded as notably superior in quality, with workmanship that fully and without reservation displays his characteristic strengths. His blades frequently remain (sound and well-preserved), a testament to the quality of his steel and forging. Tsunahiro may be regarded as a representative maker among -produced swords of the period, and his lineage's continuation through the era and beyond attests to the enduring prestige of the name he established.