The earliest dated work that survives under the name Kaneshige is a inscribed 'ei 2, 1625, by Izumi no Kami Fujiwara Kaneshige, the smith whom the published sources place directly after the Yasutsugu and Hankei. Tradition holds that he came from , where he had been a yanone-kaji, a maker of arrowheads, before going to and turning to forging blades; the Kokon Kajibikō records as much, though it is unproven. The name then carries a second smith, Kazusa no Fujiwara Kaneshige, who also signed Kazusa no Kami, the son or pupil of the first and a contemporary of Nagasone Kotetsu. The two were long treated as a single man, the old account explaining the change of title as deference: retained by Tōdō Izumi no Kami, the smith is said to have ceded that title to his lord and taken Kazusa no instead. The published sources set that story aside. Signed and age-stated works show Kazusa no was born in 'ei 3, 1626, while Izumi no Kami already bears 'ei dates, so the two are different individuals. What binds the line is its standing among the cutting-testers and the tradition that the was the teacher of Kotetsu.
The hand by which the line is best recognized is the , the rosary-bead temper of round linked in series, brought to its full form by the second generation. Over a tightly forged , slightly standing and thick with dust-fine and entering , set on the standard-width, shallow-, compact form of the years, the temper rises from a -toned base into which run linked until they become . The published sources isolate the mechanism of his hand: the are tempered in a fixed rhythm in which one element is followed by two, then one and two again, and they name this his chief point of appreciation, the feature an observer reads first. Thick enter, the is deep, the lies thick, and long and run vigorously through the temper with a bright . So closely does the result follow Kotetsu that the published sources, on one of his , judge it of workmanship that could nearly be mistaken for him, 「殆んど馬徹に見紛う程の出来」.
The under that temper is the close, well-packed of an master, in places mixed with and and tending to , with very fine applied densely and entering well. It is a controlled, urban steel, and on the second generation's larger it carries a faint standing of the grain that keeps the surface alive without breaking it up. The runs straight into a with at the point, sometimes returning rather deeply or, on his most pieces, entering the point a little before it turns. The is , finished with file marks that already carry a decorative tendency the published sources read as a prototype of the later ornamental , and the long signature is cut in a distinctive reisho clerical script, the chisel growing finer and the characters smaller in his later years.
The published sources draw the first generation's range as two manners, a distinction worth holding because it governs how his work is read. The one is a -based : a at the base, a shallow with and intermingled, entering well, the deep and bright with fine . The other is a base, broad and bearing only the faintest , the deep and the thick with set within the temper, the exceptionally clear. This second register the published sources describe as a wet -gokoro whose interior activity is especially well developed, and on a thick- of 1657 they note that, straight temper though it is, the broad tempered band is filled with vigor and the blade 「直刃といえども迫力を感じさせる」, conveying palpable forcefulness. The second generation took the linked of the first and raised it to the completed , and much recent attention has gone to sorting the two hands: the generational transition has been placed in the Keian era, the nidai is thought to have used the Izumi no Kami title first before alternating Kazusa no Kami and Kazusa no , and a signing on his behalf by Sukekurō Kanetsune, transmitted as his son, has been proposed.
What sets the line apart is best stated from its own grounded features. Its tell is the with the one-then-two rhythm, 「互の目を一つ焼くと次は二つ焼くというふうに、一つ二つと繰り返して焼く」, carried over a calm -toned base with deep and a clear , the and running long. The published sources frame the Kotetsu connection from both ends of the relationship. The they call, by the traditional account, the teacher of Kotetsu, his workmanship entirely Kotetsu-like with both and deep in and clear, 「全く虎徹のように地刃の出来が匂深く冴えている」. The nidai they place at the source of the itself: a fully realized appears on his cutting-test of Manji 4, 1661, ahead of Kotetsu's own, and from this they hold his manner influenced Kotetsu's later development of the style. The sources note the line's resemblance to the Hōjōji group active in the quarter of , with whom Kaneshige made a joint cutting-test blade, so the reads less as a single invention than as a shared current among the swordsmiths around Asakusa.
Kaneshige is rated Jō- by Fujishiro and is among the leading names, his reputation inseparable from the cutting-tests that ride on so many of his blades. The gold-inlaid of Yamano Kaemon no Jō Nagahisa recurs across his work, recording mitsu-dō and futatsu-dō cuts performed at Asakusa, and one carries a joint inscription pairing the Kaneshige line with the Hōjōji smiths over a test cut three times. On record under his name stand twenty blades at the rank, almost all and with scarcely seen, and one Important Cultural Property, a large signed held at Futarasan Jinja in Nikkō, which by its designation is patrimony preserved rather than anything that trades. The remaining blades are the realm a private collector may realistically encounter, held mostly in long-standing collections and reaching the market only at times. A signed Kaneshige bearing one of the famous Yamano cutting-test inscriptions is the example most sought, joining a documented sword to one of the most recognizable temper-lines of early .