The Ichinomiya school is a Kyoto kinko (金工) lineage founded by Ichinomiya Nagatsune (一宮長常), who was born in Kyoho 6 (1721) at Tsuruga in Province. Known as Kashiwaya Chuhachi, Nagatsune began as a gilder (mekkinshi) before travelling to Kyoto, where he studied under Yasui Takanaga, a craftsman of Goto lineage. In his early period he signed "Setsuzan", later adopting the name Nagatsune and the art name Ganshoshi (含章子). He also studied painting under Ishida Yutei, teacher of Maruyama Okyo; this grounding in shasei (sketching from life) became the distinguishing intellectual foundation of the Ichinomiya manner. At the age of fifty he received the court title Daijo, and he died at sixty-six in Tenmei 6 (1786). Members of the school characteristically bear the characters 長 (Naga-) or 常 (-tsune) in their names.
The Ichinomiya style synthesizes Goto-lineage metalworking discipline with the observational acuity of Kyoto academic painting. While Nagatsune was highly proficient in Goto-style (高彫, high-relief carving), the school achieved its renown through - (平象嵌, flat inlay) combined with (片切彫, single-cut engraving) — a technique pairing that became its signature. The preferred ground is polished (), upon which modulated chisel-work of varied intensity and rhythm produces supple, painterly line. Colour is introduced with restraint through flat inlay in gold, silver, , (素銅, plain copper), and , the limited application heightening the beauty of the ground metal. For sculptural subjects the school employs yobori (容彫, modeled relief) on ground, sometimes varying the metal between obverse and reverse in the chuya- (昼夜地, "day-and-night ground") construction. from the early Setsuzan period favour brass prepared in the kusarashi- (焼き手腐らかし地) manner, carved in with polychrome . Throughout the oeuvre, compositions unfold across front and back surfaces — continuing from the face of a onto its spine and reverse — prompting the viewer to discover the design in the round. Figural subjects draw on Chinese literary and martial themes — Guan Yu, the Three Laughers of Tiger Ravine, Huang Shigong and Zhang Liang, Ma Shi-huang, the archer Yoyuki — alongside naturalistic studies of turtles, snails, toads, and shishi, and genre scenes such as cormorant fishermen and Genroku-period Bon-odori dancers. The school's pictorial power derives from the accuracy of the underdrawing stage, where powers of observation cultivated through Maruyama-school training are evident before any chisel is taken up.
Nagatsune's eminence in the tosogu canon is encapsulated in the phrase repeatedly cited in records: "Somin of the East, Nagatsune of the West" (Higashi no Somin, Nishi no Nagatsune). Together with Tetsugendo Shoraku and Otsuki Mitsuoki, he was further lauded as one of the "Three Great Masters of Kyoto metalwork" (Kyoto kinko no sanketsu). The consistently praise "the outstanding pictorial power developed through studying Maruyama-school painting and the assured carving technique that elevated his reputation." His Fukurokuju on is singled out as a piece in which "the excellence of the master craftsman Nagatsune is vividly on display," while the "Bounty of the Sea" in chuya- construction is hailed as "a masterpiece that fully reveals the stature of Nagatsune, who was lauded as the Western yokozuna." The Four Divine Symbols , inscribed "Carved in leisure" (kandori kore o horu), is a painstaking work made to the artist's own taste in intervals between commissions. From the robust of his early Setsuzan-period through to the refined and flat inlay of his mature years, the Ichinomiya corpus attests to an artistic range and technical command that secured for its founder a permanent place among the foremost metalworkers of the period.