In rebuilding Japanese industry after WWII but for peaceful purposes, one avenue that was exploited was the manufacture of musical instruments. Pre-War there had been a few well respected makers like Suzuki, so there was some skill available and it must have seemed like a safe idea - Until it killed Chicago (and a lot of other US) manufacturing!
Nakanishi Musical Works Martin Copy
Once in business, distributors found that giving the Ukuleles they produced Western Brand names was a better way to sell them, (somewhat similar to Chinese brands of today). Sometimes, with the older, long standing ones like T&D or B&J, they used old brand names they had used on Chicago made Ukuleles before the war. I have read that there were 80 firms started in Japan in the late 50's and early 60's to service the fretted chordophone boom but by 1970 50 of them had gone bankrupt! As far as I can see the same brand name may have been given to Ukuleles from a number of factories and each factory may have produced a number of brands, including some branded with their own Japanese name. This post war production was primarily Sopranos and Baritones, (I've only seen a couple of Concerts and Tenors), and mainly from Japan, with a few examples coming from other countries in the region. The Ukuleles themselves vary in quality from very low end to fairly high quality and some of these brands are now well respected internationally as makers.
Originally founded in the 1930's by Mitsuo Matsuki and Atsuo Kaneko, (who later helped found Teisco), making Guitars branded Guya for the Japanese market. Production stopped for WWII and after the war Matsuki started up again founding first the Tokyo Sound Co. and in 1956 founded Guyatone. They were the first Japanese manufacturer to sell their own brand named instruments to the American public, but the were also heavily involved in the Japanese OEM production of the 60's and 70's, producing a lot of different brands of Guitar certainly, for a lot of different people, (It's much harder to say about the Ukuleles and most information is only about the Guitars. It is possible they never made any Ukuleles but there are some brands that they are down as the only producer of?) In 1995 Mitsuo Matsuki died and in 2013 Guyatone separated from Tokyo Sound Co. to become an independent firm mainly making Guitar effects pedals.
When they were doing the OEM work they produced instruments branded Antoria, Barclay, Broadway, Coronado, Crestwood, Delta, Futurama, Guyatone, Howard, Hi-Lo, Ibanez, Ideal, Imperial, Johnny Guitar, Kent, Kingston, Lafayette, Lake, Montclair, Omega, Orpheus, Prestige, Royalist, Saturn, Silhouette, Silvertone, Vernon, Winston, Zenta and probably produced Beeton, Bradford, Canora, Maxwell and Regent. This may not be all the brands they made, I haven't seen all of these names on Ukuleles and they may not have been the only firm producing them?
They started out in the early 1900's as a maker of Japanese cabinets and after WWII they stared making cabinets for thing like radios and amps, (and sewing machines). In 1951 they were taken over by Singer Sewing Machine Co. but in the 60’s Singer moved the cabinet making to the Philippines so they had to find new products. Guitars were big at the time and they had some in house expertise, but because they were late to the market they worked on making quality rather than budget instruments. They did OEM work for lots of people including some of the other Japanese OEM firms who could do the budget work but subcontracted the top quality manufacture, it wasn’t until 1979 that they started they own house brand, Westone. With OEM Guitar making moving to South Korea and the decline in domestic sewing machines Singer could no longer have a Guitar maker on its books so after failing to buy itself out Matsumoko was closed down.
While there were in business they produced instruments branded Apollo, Aria, Arita, Barclay, Burny, Capri, Columbus, Conrad Country, Cutler, Dia, Domino, Electra, Epiphone, Granada, Hilo, Howard, Lindberg, Lyle, Luxor (not the Horenstein Brand), Maxitone, Mayfair, Memphis, Montclair, Pan, Raven, Stewart, Tempo, Univox ,Vantage, Ventura, Vision, Volhox, Westbury, Westminster and possibly made Bruno, Crestwood, Conqueror, Eros, Mako, Memphis, Orlando and Toledo. This may not be all the brands they made, I haven't seen all of these names on Ukuleles and they may not have been the only firm producing them?
Nakanishi Musical Works
Established in Konan City, Aichi Prefecture in 1958 by Seiichi Nakanishi this wasn't a mass producer of instruments it was more like a high end luthiery workshop making acoustic Guitars, Mandolins and Ukuleles. Most of its output was copys of Martin instruments for the Japanese and later when Martin themselves stopped making Ukuleles, some export to the US. For a while Seiichi Nakanishi was considered the best luthier in Japan and some of his former employees, having learned luthiery from him went on to start their own workshops, people like Shinji Takahashi with T's Guitars and Ukuleles and Hayato Shiiba with the Shiihara Ukulele Factory. Seiichi Nakanishi died in 2013 but had retired and closed the workshop some time before that, (possibly before 2005), it is worth noting though that at the end of the workshops run the output was almost entirely Ukuleles