The school was founded by Hashimoto Shinzaemon, known as the first-generation , who served as a retained smith of the Nabeshima domain. In Keicho 1 (1596), by domain order, he entered the school of Myoju in Kyoto together with his kinsman Munenaga -- to study sword forging, Munenaga to learn carving techniques. They returned to in Keicho 3 (1598) and established themselves in the castle town below Saga Castle, where under sustained Nabeshima patronage the school prospered greatly. The main line passed through three generations of exceptional accomplishment: the , who received the title Daijo and changed his name to Tadahiro in Genna 10 (1624); the second-generation Omi Daijo Tadahiro, who over a career exceeding sixty years left behind the greatest number of extant works among all smiths; and the third-generation Mutsu no Kami , whose workmanship the situates as closer to his grandfather than to his father, possessing "a bold, vigorous, and unconstrained character." Alongside the main line, the soba- ("side-") smiths -- most prominently the two generations of Kawachi Masahiro, together with Dewa no Kami Yukihiro and the shadowy Yoshiie -- produced works of consistently distinguished quality while maintaining their own individual signatures within the school's shared aesthetic.
The defining technical hallmark of the school is the ("rice-bran texture"): a tightly forged upon which extremely fine adheres thickly in -like particles, with delicate entering well and the steel appearing bright and clear. This forging -- consistently praised as among the finest in the tradition -- constitutes the school's unifying signature from the 's earliest works through the latest productions of the collateral lines. Upon this foundation, the school's principal expressive modes divide between and . The main line excelled above all in : a deeply -laden, -rich hardening in which fine and run through a bright and clear -- tempering that the imbued with a "tasteful, somewhat archaic flavor," that the nidai refined into a deep, band-like clarity of unwavering consistency, and that the elevated to its most powerful expression, with forging the judges as "even stronger" than the founding generation's. In , the nidai Tadahiro produced flamboyant tempering with long and , the relatively aligned, at times achieving the layered-flower (juka) effect -- a mode that the soba- masters made their particular strength. Masahiro "favored -ba" over the main line's , tempering in which is mixed with and , with deep , thick , and conspicuous producing "a flamboyantly undulating pattern that is richly animated." Yukihiro developed a distinctive vertically elongated with characteristically long , a style described as "overflowing with spirited force." Yoshinobu, the 's adopted son-in-law and father of both Masahiro and Yukihiro, is recognized as "a pioneering example of the style later broadly termed soba-."
The school occupies a position of singular importance among swordmaking traditions. Its founding act -- the 's absorption of Myoju's refined forging techniques and their translation into a new provincial school under domain patronage -- established a paradigm of institutional swordmaking that sustained continuous, high-quality production across multiple generations and collateral branches. The 's recurring verdict across all branches of the tradition is one of exceptional refinement: and that are "bright and clear," that is invariably , and works that are -- sound and well-preserved -- in condition. That the third-generation 's extant works are comparatively scarce because he served as for his father, that Yoshiie "lived continually in the shadows" as substitute maker for the first two generations, and that collaborative works between father and son survive in meaningful numbers all testify to the depth of the workshop system that sustained the tradition. From the 's Keicho-era foundations through the school's mature production in the and Genroku eras, the lineage represents the most fully realized expression of domain-patronage swordmaking in the Japanese tradition.