The first-generation Harima Daijo Tadakuni was the second son of Soemon Hirosada (also known as Yoshiie), who was a disciple of the first-generation , and styled himself Hashimoto Rokurozaemon; his elder brother was Kunihiro. Because he shared the Hashimoto surname with , it is thought they may have been of the lineage. The earliest extant dated work bearing the title Harima Daijo is from 'ei 13 (1636), indicating he received that court title before that year; he was later promoted to Harima no Kami. He was retained by the Ogi domain, one of the three branch domains of the Saga Nabeshima house, and served as an Ogi-domain smith. In his later years he took tonsure and adopted the go Kyutetsu, with works extending into the Tenna era (1681-1684). The second-generation Tadakuni, his son, styled himself Danzaemon and initially signed Harukuni before succeeding to the name Tadakuni, with dated works spanning Enpo 5 through Jokyo 2; in the great majority of his swords he cut a chrysanthemum crest on the and a crab-and-peony crest (kani--) on the , likely indicating a close connection with the Konoe family.
The Tadakuni lineage is distinguished by two principal modes of workmanship. In , the characteristic expression is a -dominant pattern mixed with , angular elements, and -like forms, with long entering well and intermingled. The is deep, adheres thickly, and conspicuous runs vigorously throughout the tempered area with appearing -- this profusion of being the most striking habitual trait of the Tadakuni hand and the feature by which this smith is most readily distinguished within the school. In his most ambitious works, and combine to produce , a manner scarcely seen in the period. The is an excellent, finely compacted with extremely fine adhering thickly without forming , and fine entering -- clearly displaying the school's hallmark forge. In , the is bright, attaches evenly, and fine and appear, producing a calm and restrained that is likewise highly accomplished.
The first-generation Tadakuni's - with strikingly high is described as deliberately evoking the manner of old works, blending boldness with florid brilliance and commanding spirit. Even when the temper extends nearly to the , the remains refined and the adheres evenly, showing no breakdown in the relationship between and . The second generation, while producing comparatively few surviving works, demonstrates technique that in places surpasses that of his father, establishing him as one of the foremost smiths of his time. Together, the two generations represent a lineage in which the technical mastery of the school is expressed with distinctive individuality, their works consistently praised as clear in both and and of outstanding workmanship.