Kunitsugu (来国次) was a swordsmith of the school in Yamashiro Province, active from the close of the period into the opening years of the . He is traditionally identified as a disciple of Kunitoshi, with one lineage account holding that he was a cousin of Kunimitsu; another tradition records him as a son of Kunitoshi and younger brother of Kunimitsu. Together with Kunimitsu, he stands as a representative figure of the school in its final -period flowering. Since ancient times he has been counted among the Masamune Juttetsu — the Ten Great Disciples of Masamune — and bears the distinctive epithet " ," a designation reflecting his pivotal role in absorbing the vigorous - aesthetic into the refined idiom of the Yamashiro tradition. Signed by his hand are exceedingly scarce; the great majority of his extant oeuvre consists of and , while surviving examples in forms such as and are of the utmost rarity. Among his few dated works, a inscribed "Karyaku 2" (1327) represents the earliest known chronological anchor for his production.
The technical hallmark of Kunitsugu lies in the synthesis of -school orthodoxy with characteristics previously unseen in the lineage. His is typically a well-consolidated , frequently mixed with and occasionally showing — a subtle standing of the grain. Fine, thickly applied adheres throughout the ground steel, with entering prominently and standing out with clarity, producing a bright and luminous . His ranges from mixed with and in his more restrained mode to boldly tempered -ba combining , , and with vigorous internal activity. In both modes, the is characteristically strong: adheres thickly, and course through the tempered edge, and the achieves a bright, crystalline clarity described repeatedly in official assessments as . The varies from with turnback and to with a pointed tendency, reflecting the breadth of his working range. Notably, his early signed — identifiable by vertically elongated, fine-chisel signatures on — exhibit a more restrained, elegantly slender form with calm that strictly observes tradition, while his mature work embraces the broader, more powerful of the late to early transition.
Kunitsugu occupies a position of singular importance in the history of the Japanese sword as the figure through whom the aesthetic entered and transformed the Yamashiro tradition. His finest works unite the luminous and structural clarity of the school with the powerful formation, dense , and dynamic associated with the lineage, achieving a synthesis that neither school alone could produce. The range of his surviving works — from calm, dignified pieces preserving pure character to vigorously tempered -ba blades fully manifesting influence — provides indispensable material for understanding the evolution of forging practice across the - divide. Distinguished provenances further attest to the esteem in which his work has been held: blades traced to the Tokugawa shogunal house, the Maeda, Uesugi, Asano, and Yamauchi families, and pieces bestowed by figures such as Tokugawa Tsunayoshi and Matsudaira Nobuyasu. That his works have consistently been judged — sound and well-preserved in both and , with ample — speaks not only to the quality of his steel but to the reverence with which successive generations of custodians have maintained these blades.