Xenoah was a brand of derailleurs produced in Tokyo. It grew out of the DnB brand, possibly as a result of the takeover of DnB by the Fuji Motors Company.

Some of the story may go something like this:

• Dai Nippon Bicycle (DnB) were a Tokyo based manufacturer of bicycles. In the 1950’s there seems to have been two centres of bicycle industry activity in Japan, Tokyo was one, and Sakae near Osaka (the home of Shimano, SunTour, SR and Sugino) was the other. A certain Mr. Miyata (a name with resonance) from DnB seems to have been an influential figure in the Tokyo group.
• Derailleurs branded DnB were produced by a company called Dai Nippon Kikai Kogyo Co., Ltd, which was presumably the same as or related to Dai Nippon Bicycle.
• Hiroshi Nakamura claims DnB released an ‘A Type’ non-parallelogram derailleur in 1957.
• Hiroshi Nakamura also claims that DnB released a parallelogram model as early as 1958. I believe that this parallelogram model was a copy of the Campagnolo Gran Sport.
• In 1965 I believe that DnB released the DnB 66 model in this collection.
• At some point in the late 1960s I believe that DnB began to use the ‘Danube’ brand, producing both derailleurs and bicycles with this brand. This brand appears to have been owned by the Fuji Motors Company of Tokyo, which morphed into a company called Xenoah.
• The 1971 edition of Japan's Bicycle Guide shows a funky looking derailleur called the DnB Danube alongside the DnB 66.
• The 1975 edition of Japan's Bicycle Guide shows a completely new range of three derailleurs, all of which use a dropped parallelogram design. In the book thay are called 'GX Xenoah Model RD 18-1', 'GX Xenoah Model RD 18-2', 'Danube Xenoah RD 17'.
• And then the 1976 edition of Japan's Bicycle Guide reverses utterly, omitting all the new, modern, 1975 models, and showing only the, 1960s era, DnB 66.

The Xenoah company exists to this day as Zenoah, and is part of the Husqvarna group.