How many bike makers were there in Japan? I don't know of many. The US importers invented a lot of names. Nishiki is one of those. Even Fuji was, as far as I know.

The only makers I can think of are/were Panasonic, Bridgestone, Kuwahara, and Tsunoda. All those other Japanese names weren't the names of Japanese companies.

Shimano doesn't make stuff in Japan any more, as far as I know. They survived because they are, by far, the biggest bike parts maker in the world. I believe they're also pretty big in their other business, fishing tackle.