Yamato no Kami Yasusada is a - master of , by common name Tomita, sometimes written Tobita, Sōbei, born in Genna 4 (1618) and at work from the Keian years into Enpō. A surviving inscribed as made at the age of fifty-three in 10 fixes that birth date, and a Keian-dated blade signed as made in shows that he had already reached by Keian 1 (1648). The published sources long held him a smith of and a pupil of Yasutsugu, but recent research and the swordbook Ben'gi place him instead within the Kishū Ishidō group, recording him as a resident of who belonged to the Ishidō house and signed the surname Tomita, and noting elsewhere "Yasusada, of Kishū." An extant signed at Wakayama in Kishū, and the shared Tomita surname of the Kishū smiths Tameyasu and Yasuhiro, make the attribution persuasive. On the evidence, together with the tapering long and the Yamano-family cutting-test inscriptions his blades so often carry, the prevailing view makes his teacher Izumi no Kami Kaneshige rather than Yasutsugu.
The tell of his hand is the temper. Over a tight he works a notare base into which is mixed, and the feature the judges grasp as his own is the way that line turns angular: the boxes at its peaks and the squares at peak and valley, what the published sources describe as the hardened edge taking on an angular, boxed configuration. A notare base carries the larger part of his record, at times widening into a broad , with entering, the deep, the thick and in places gathering coarse. Fine run through the temper and small enter, the activity of a -based hand rather than a one. The runs to a , sometimes shallow and wet-looking, sometimes with a slightly long turnback. The blades are robust of the form, wide at the base with a marked taper to the tip, thick in , shallow in , the compact, and the conspicuously high of his construction is itself one of his marks.
The is the constant beneath that varied edge. His is densely forged, at times mixed with and flowing in places, the adhering thickly and at its finest laid dust-fine, with delicate entering well and the steel clear. The published sources single one blade out for a "truly of excellent quality," the fineness of its and revealing a high level of forging skill. Over it the deep, bright and the well-adhered give the temper its clarity, and where the hardening rises high the mixes with pointed elements and some height variation, the at times keenly clear and at times, on the wider-tempered pieces, tending toward a subdued . It is a single hand worked in clear, vigorous steel.
The published sources divide his work into two manners, and they say which is the more numerous. The first is the mixed with that turns angular, the larger part of his record; the second is a -dominant , tempered high and wide with pointed elements, fewer in number but distinct. His full maturity is placed in the Manji years: the commentary states plainly that his works span Keian through Enpō but that "the Manji era is regarded as his fully matured period, when many of his most spirited pieces were produced." His blades carry dates from Meireki and Manji into , and the run of Yamano cutting-test inscriptions, by Yamano Ka'emon Nagahisa and by Kanjūrō Yasuhisa among them, ties his record to the testing of a sharp-cutting hand.
What the judges return to, again and again, is his standing beside Kotetsu. They read his work as approaching Kotetsu and as resembling yet distinct from him, calling one blade an appearance that resembles yet differs from Kotetsu in his so-called phase. The distinction is drawn not by borrowing Kotetsu's traits but by naming Yasusada's own: where Kotetsu's hand is read as the brighter and clearer, the published sources find that beside Kotetsu "the conspicuous prominence of the is a point of appreciation" in Yasusada, and that the boxy angular , the steeply raised , and the way the temper near the grows calmer than elsewhere are where his individual character is caught. He stands among the leading - smiths, beside Kotetsu and the Hōjōji line, his -leaning temper inherited from Kaneshige and worked into a form that is his own.
Yasusada is graded Jō , and his signed and dated survive in comparatively good numbers, well represented at the rank, the present record running to a dozen blades from the fourteenth session through the sixty-second. The published sources call his finest the typical and representative work of this smith, one "a superior piece with much to appreciate," both and bright and clear, robust and of considerable length, another "a textbook-typical and representative work" displaying his favored manner. He has no works in the National Treasure or higher modern designation tiers; his standing rests on this body of and , several bearing the prized Yamano gold-inlaid cutting-test inscriptions that make them valued reference material as well as fine swords. Recorded ownership of his blades is sparse, scattered private holdings rather than great institutions, so a signed Yasusada is not beyond reach in the way a master is. It comes to a private collector from time to time, a robust of the capital whose angular and Yamano cutting-test inscription set it apart from the Kotetsu it is so often measured against.