Aoso-Za (The Guild Of Aoso [Boehmeria Nipononivea, A Fiber Material For Clothing]) (青苧座)

"Aoso-za" refers to "za" (the guild) of "aoso" (Boehmeria nipononivea, a fiber material for clothing), which was established in the later middle ages of Japan. Well-known major aoso-za existed in Echigofuchu (the then aoso-producing area, now part of Joetsu City, Niigata Prefecture), in Omi Sakamoto (the then midpoint of the aoso distribution network, now part of Otsu City, Shiga Prefecture), and in Kyoto and in the area now called Tennoji Ward, Osaka (then both aoso-consuming cities).

Summary

It is unclear exactly when aoso-za was established. But at least, it must have been established before the position of "honjo" (proprietor or guarantor of manor) was transferred around 1383 from the Ogimachisanjo family to the Sanjonishi family (relatives of the Ogimachisanjo family).
It seems to have been born of aoso merchants linked with government officials who had strong connections with the Ogimachisanjo family

Utilizing the position of honjo, the Sanjonishi family set up some checkpoints around Kyoto; for example, in Moroguchi, in Tanba Province (the area that includes today's northern part of Kyoto Prefecture), in Mino Province (part of today's Gifu Prefecture), and in Omi Sakamoto, and dispatched local governors there. With these measures, the Sanjonishi family collected "kuji" (temporary tax) from aoso merchants who passed through those checkpoints, and the kuji imposed on aoso merchants was called "so-kuji." Meanwhile, aoso-za gained the exclusive right of selling aoso in exchange for the payment of so-kuji. Among others, "Tennoji so-za" (the guild of aoso in Tennoji) had a particularly powerful voice within the aoso community. It is firstly because Tennoji so-za had an almost exclusive right of purchasing aoso from "Echigo so-za" (the guild of aoso in Echigofuchu [the aoso-producing area]).
And secondly, Tennoji so-za also had an almost exclusive right of selling aoso to "Sakamoto so-za" (the guild of aoso in Sakamoto) and to "Kyochu so-za" (the guild of aoso in Kyoto)
In short, Tennoji so-za monopolized the distribution network of aoso from Echigo Province to the "Kinai region" (the five provinces surrounding Kyoto and Nara). To keep its monopoly, Tennoji so-za paid the tax in kind in an amount of as much as 562.5 kg annually to its honjo Sanjonishi family in exchange for the exemption from so-kuji that it paid when passing through the checkpoints. During the Tenmon era (A.D. 1532 - 1555), so-kuji was imposed also on the growing aoso-producing areas, such as Kai Province (the present Yamanashi Prefecture) and Shinano Province (almost the same area as that covered by the present Nagano Prefecture).

However, when the Nagao clan, which assumed "Shugodai" (deputy of 'Shugo' [provincial constable]) of Echigo Province, gained control of the province administration around 1497, the clan did not permit Tennoji so-za the exclusive aoso-purchasing right. And after the Eisho War, the Nagao clan made the Uesugi clan (the Shugo of Echigo Province) its puppet, and it also began to exert its control over aoso-za. During the Daiei era (A.D. 1521- 1528), the Nagao clan gave both the kuji collection right and the distribution control right of aoso to the Kurata clan, which was "tonin" (the director) of Echigo so-za. And the Nagao clan forced the Sanjonishi family not only to reduce the tax in kind, which was paid by Tennoji so-za, to 187.5 kg a year, but also to allow Echigo so-za to transport aoso into Kyoto. This tendency was accelerated after Kagetora NAGAO (more commonly called "Kenshin UESUGI") succeeded to "Soke" (the head family or house) of the Uesugi clan. During his reign, he imposed the tax on the merchants who came by sea to Echigo Province from other provinces for aoso, thereby gaining control over the distribution network of aoso from Echigo Province to the Kinai region. And it was the above-mentioned Kurata clan that was actively involved in this aoso trade. The Kurata clan unified the aoso merchants in Echigo Province, and backed up the military activities of Kagetora NAGAO (Kenshin UESUGI) in economy as its purveyor.

Afterward, za was abolished by "the Shokuho regime" (the regime of Nobunaga ODA and Hideyoshi TOYOTOMI; "Shoku" and "ho" are the initial letters of Oda and Toyotomi), and the territory of the Uesugi clan was changed, so that aoso-za in Echigo Province lost its influence. And ironically, the aoso in Echigo Province is said to have gotten the finishing stroke during the Genroku era (A.D. 1688 - 1704) of the Edo period in the loss of the competition over aoso with the Aizu domain and the Yonezawa domain, into which the cultivation techniques of aoso were introduced when the Uesugi clan had its territory changed.