Two distinct smiths bear the name Sadakuni in the designation records. The first and more prolific is Daijo Fujiwara Sadakuni, a swordsmith of the Shimosaka group in province who had the closest connection with Yasutsugu. Since the period there have been almost no entries for him in sword books or signature compendia, and details of his life remain unclear. For a time, because the manner of signing " Daijo" and related features closely resembled those of Yasutsugu, there existed a theory identifying the two as the individual; however, the prevailing view today understands him as a smith of the Shimosaka lineage. Among what are thought to be his early works are pieces signed " no Shimosaka Sadakuni," and a bearing a date of Keicho 14 (1609) establishes his period of activity. He is said to have initially provided carvings for the first-generation Yasutsugu's sword work, and his specialty in plum and bamboo motifs may represent the source of -bori carving style. He probably had a falling out with Yasutsugu and remained in for life. The second smith is Tajima no Kami Hojojji Tachibana Sadakuni, a capable maker of the Hojojji group active around the Manji and eras. His earliest dated work bears a Manji 3 (1660) inscription, placing his activity slightly before the period and chronologically after the first-generation Omi no Kami Hojojji Masahiro. A second generation of Daijo Sadakuni is also recognized, distinguished by large characters cut with thick chisel strokes.
Daijo Sadakuni's workmanship differs to some extent from Yasutsugu's. The darkened characteristic of Yasutsugu is seldom seen; in general the forging is densely worked, and compared to ordinary works his presents a relatively refined that constitutes a principal point of interest. His is predominantly -based, with slight , small , and a gentle impression in the of both and . The characteristically shows a tendency. While he excelled particularly in , he also demonstrated remarkable range, producing flamboyant centered on with deep , thick , and vigorous and . His , whether depicting the Fudo Triad, , or auspicious crane-and-turtle motifs, display the distinctive power of carving and are thought in some cases to have been executed by the smith's own hand. Tajima no Kami Sadakuni of the Hojojji group displays the representative features of his school: finely compacted with dense, extremely fine and plentiful fine ; a -based temper with and ; and a that is deep, with thick , presenting a bright, clear appearance.
Both smiths named Sadakuni are recognized as makers of outstanding skill within their respective lineages. Among Daijo Sadakuni's surviving works, the breadth of his artistic range is particularly noteworthy: from restrained pieces conveying a subdued, austere flavor to boldly tempered that indicate the full extent of his ability. His dated works and distinctive carvings provide valuable documentary evidence for the study of early swordmaking in . Tajima no Kami Sadakuni, though comparatively few examples are seen within the Hojojji group, produced works of excellent workmanship that approach the level of the Nagasone lineage. A bearing a gold-inlaid inscription recording a mitsudo cutting test by Yamano Ka'emon Nagahisa in 5 (1665) provides valuable reference material for the study of both the smith and the school.