The Iwamoto school was a house of (町彫) metalworkers, founded in the early eighteenth century by Iwamoto Chūbei, a pupil of the Yokoya school, and continuing through eight generations of headmasters. As the state repeatedly, "the Iwamoto line was originally of the Yokoya tradition," and the school's history turns on a succession crisis within that lineage: when the fifth-generation master Ryōkan died young, his junior fellow-disciple succeeded as sixth head of the Iwamoto house. This was Iwamoto Konkan, born in in Enkyō 1 (1744), whose original family name was Asai and who first used the name Ryō (also read Ryōun) before changing it to Konkan. Although heir to a Yokoya-affiliated house, Konkan "studied the carving methods of the Nara school, centering on Yasuchika, and what he achieved by incorporating the strengths of both the Yokoya and Nara traditions is precisely Konkan's art: thoroughly Edomae in its stylish, urbane (iki) sensibility." He also signed with the art names Shunshōdō (春曙堂) and Hakuhōtei (白峯亭). The line continued through Iwamoto Kanri, common name Kijūrō, who first studied under Konkan, was later adopted by him, and succeeded as seventh head; the school's orbit also included the pupil Konju, who lived at Kōjimachi in .
The school's collective style rests on this synthesis of Yokoya sculptural discipline and Nara-school carving methods. Its preferred vocabulary is (赤銅) with (魚子地) ground, worked in (高彫) high relief with suemon-zōgan (据紋象嵌) and polychrome (色絵) in gold, silver, (四分一), and (素銅) copper; but the attest an unusually broad range of grounds — and iron in polished (磨地), - (縮緬石目地), brass , and gold — together with (鋤出彫), sukishita-bori, relief-carved openwork, fine (毛彫), and inlaid (青貝) mother-of-pearl, set even into the eyes of fish. The distinctive triangular chisel (sankaku- 三角鏨) recurs as a house hallmark, as does a masterful command of negative space and calculated composition, with obverse and reverse conceived in deliberate contrast. Favored subjects are drawn from nature observed with startling fidelity: the uo-zukushi (魚尽) arrays of fish "rendered with such precision that one feels each individual species could be identified," each scale and backbone carved line by line; herons among reeds; pheasants under a hazy moon; carp gliding through waterweed; alongside shishi, orchids, chrysanthemums, dragons, landscape narratives such as cormorant fishing and the Chōfu Tamagawa, and even Buddhist imagery of Dainichi Nyorai and Niō. The judge Konkan to have "ranked among the foremost artists of the naturalistic, sketch-from-life approach," while a fully matched -crest mounting shows the school equally capable of orthodox, formal commissioned work.
The Iwamoto school's place in the tosogu canon rests above all on Konkan, counted among the leading metalworkers and habitually praised in the with the phrase "Edomae no iki" — the quintessential stylishness of ; his fame is further reflected in the extensive forgery of his signature. Works transmitted in the Tsugaru and Sakai families attest the esteem his oeuvre commanded. The tradition did not end with him: Kanri "followed his teacher's manner closely and, after Konkan, produced a number of powerful works," while Konju's carving, "taut and controlled" in the master's likeness, carried the inlay-centered methods forward. Wide-ranging in subject and prolific in output, the school stands as one of the defining expressions of late- art — a lineage in which the strengths of the Yokoya and Nara traditions were fused into a single, unmistakably urbane style.