Thank-you for posting the derailleur image. I had forgotten that they produced derailleurs. One piece of literature that I have for a pull-chain model (it looks like it might be the same model as the cut off image of your post) states that it came with a three speed freewheel. I wonder if they also made the freewheel or had it sub-contracted? In addition to Shimano and SunTour, there were multiple cog freewheels from DNB and Sanko at the time, so neither approach would surprise me.

There's another Japanese company named Arai that manufactures motorcycle helmets. Given that bicycle companies were often involved in the motorcycle industry and that the helmet company also traced their origins back to the very early 20th century, I used to think there may have been some ties between the two but that does not appear to have been the case. It's not surprising that there are multiple Arai companies, when you consider that it is a fairly common Japanese surname.