Ikkanshi Tadatsuna is the second-generation Ōmi no Kami Tadatsuna, son of the Ōmi no Kami Tadatsuna and one of the representative Osaka smiths of the Genroku years. The published sources record his common name as Mantayū, that he succeeded his father as the second to bear the title Ōmi no Kami, that he claimed descent from Kunitsuna and so prefixed to his signature, and that around Genroku 2 he began to style himself by the Ikkanshi. They place him among the leading Osaka makers of his day, one who is, in their words, "renowned for the brilliance of his and and the decorative beauty of his carving". His early manner follows his father closely, and the heart of his record is the broad, signed and dated that doubles as a field for the carving on which his fame chiefly rests.
His characteristic hand is read first in the temper. Over a tightly forged he opens a straight at the base and then runs two related manners. The earlier and more inherited of them is a with well-aligned and long , the very style in which the excelled, the long entering and the and cutting across them. The published sources call him "a master who surpassed his father", and they locate the difference precisely: where the first generation's is aligned and dignified, the nidai's is deeper in , brighter in and firmer in , talent they name shutsuran, the dye that outdoes the indigo.
His mature and most personal manner is the , the surging-wave temper collectors know as . The published sources tie it to the Tsuda Sukehiro circle and call it on one his "favoured Tsuda-style tōran temper". Over the tight , the applied thickly in minute particles and fine entering, he builds a shallow base mixed with and -like elements that swells into the wave, the long still entering, the deep, thickly adhered, and running frequently, the bright and clear. The is a shallow to with . A quieter survives on a small number of blades, the calmest and rarest of his three faces, set over the same bright .
That is the constant beneath all three manners. The forging is a tightly and finely packed, the gathering thickly and at its best falling in minute particles, with fine threading the surface, the steel bright and clear. It is the well-made Osaka rather than a rustic one, and it is the field his temper and his carving both sit upon. The reference texts list his oeuvre as the aligned after the , the tōran, and the occasional , all opened from the long straight that marks the Osaka start.
What sets him apart, more than any single feature of or , is the carving. The published sources treasure his as Ikkanshi-bori, recording that he "earned a high reputation for surpassing his teacher, and his blade carvings in particular are admired and treasured as Ikkanshi carving"; "his blade carving is skillful and is treasured by the world as Ikkanshi-bori". He cut a relief -no- within the groove, the -, jewel-chasing dragons, and the -no-takinobori, a carp ascending a waterfall that the sources believe he was the first to attempt and which they note has "not been encountered on any of his blades other than this one". He worked closely with the Osaka carving master Fujita Tsūi, and he cut the added inscription dōsaku to mark the carving as his own hand, a feature, the sources observe, not seen on the at all and one that established a model within .
For the collector Ikkanshi Tadatsuna is a leading Osaka name whose work can still be sought, though the very best is held rather than traded. Fujishiro grades him Jō-jō . He has no National Treasures; his record runs instead through the rank in number, with several pieces reaching and a long signed raised to Important Cultural Property. The published sources call one of his a representative work from the period when he was at the height of his powers, excellent in both and , its Ikkanshi-bori exceptionally splendid. About fifty-two of his blades stand in the and tiers, with a recorded example held by the Kyoto National Museum and a documented blade once in the keeping of the Asai house. Because his work is signed and dated and survives in fair number, a Tadatsuna comes to light more readily than most Osaka masters of his rank, yet a dated carrying his own Ikkanshi-bori is a landmark when it appears, and the finest, with the carp and the cut by the smith himself, are documents of the carving craft at its Osaka height.