Nihon Shōkai
The name Nihon Shōkai (日本商会) appeared in some ads related to the Walz company. It seems that it was the distributor at least of the original Walz camera (see this 1937 ad, but its name does not appear in a Dec 1936 ad in Asahi Camera) and of some wartime variant of the Waltax (see this ad and this ad). In the case of the wartime Waltax ads, its name appeared side by side with the name of the distributor Honjō Shōkai, explicitly mentioned as a wholesaler (本庄商会卸部). The latter company still exists as Honjō K.K. (本庄株式会社), a photo wholesaler (see the company history here). The two same names also appeared as special agents on a wartime ad for the Mamiya Six II and III, in the 22/12/1943 issue of Asahi Graph (see here). In the ad were also offered some Walz filters and a Walz hood for the Mamiya Six.
This Japanese page at La Chambre Claire suggests that Nihon Shōkai was the owner of the Walz brand name before the war, and became Walz Shōkai after the war.
