The school (江川) traces its origins to Province, though its defining master, Toshimasa (江川利政) -- also known as Katsura Sorin (桂宗隣) -- was born in Mito in An'ei 2 (1773). Toshimasa traveled to and entered the atelier of Yokoya Eisei (横谷英精), placing himself within the Yokoya lineage of iebori (hereditary atelier carving). His promise was recognized by a senior fellow student, Katsura Eiju (桂永寿), who adopted him into the Katsura house; Toshimasa thereupon succeeded that family and, like Eiju, became a retained craftsman (kakae-ko) to the Arima family, lords of Kurume Domain. He used both the and Katsura surnames throughout a remarkably long career: dated works are recorded at ages seventy-five, eighty-one, eighty-two, and even eighty-eight -- testament to a creative life spanning the breadth of the late period. The "Toshi-" prefix visible in members' names suggests a hereditary lineage consciousness within the school.
The technical vocabulary of the school is rooted in the Yokoya tradition yet distinctly individual. The characteristic ground is , though silver and (朧銀, hazy silver alloy) grounds appear with equal authority. Upon these prepared surfaces, the school deploys (高彫, high-relief carving) of pronounced volume and powerful modeling, enriched with (色絵, polychrome inlay) in gold, silver, and , frequently supplemented by - (据文象嵌, applied-relief inlay). The repertoire of subjects is wide and literarily grounded: tigers in the mizunomi-tora (水呑虎) convention; peonies and shishi-lions in the idiom at which "the Yokoya school excelled"; Rokkasen (Six Immortal Poets) programs with carved in solid-gold yobori (容彫, sculptural carving); Monogatari scenes of Narihira's ; and landscapes evoking poetic locales such as Noji no Tamagawa and Noda no Tamagawa. A notable vein of naturalism runs through the corpus: the mushi-zukushi (insect ensemble) distributes twenty-two insects across an entire mounting, with "careful naturalistic observation" providing "the foundation for expressing both motion and stillness." In pictorial composition, the school characteristically employs mist () to organize dense, sumptuous surfaces -- the (One Hundred Flowers) avoids "any sense of disorder through the skillful placement of mist." Iron grounds also appear, worked in with openwork () "skillfully exploited to heighten the narrative quality," as in the tiger with its delicate water ripples and drifting haze. While grounded in the Yokoya iebori tradition, the school's choice of subject and modeling also reveal "the fresh, innovative sensibility associated with ," the town-carver idiom.
The school occupies a distinctive place in the late- tosogu canon as a bridge between the orthodox Yokoya atelier inheritance and the expressive freedom of the world. In examinations, Toshimasa's works have been recognized for their elevated dignity appropriate to equipment, their courtly, graceful sensibility, and their sumptuous yet disciplined pictorial programs. The is called "the finest () among his works," while the Rokkasen set is praised as a work "in which Sorin's true merits are fully realized." Even pieces produced at advanced age -- the tiger and made at eighty-one -- display "exceptionally fresh" workmanship, "clearly manifesting Katsura Sorin's high level of technique and artistic sensibility." That these works span formal of "notably elevated dignity," unified - suites, and intimate pictorial alike demonstrates the school's comprehensive command of the kinko metalworker's art.