There is one more website I would like to mention. Information in English on Japanese companies is getting a little bit easier to find than in the past, but is still not what it should be. I just came across a website called Funding Universe and for some reason they have a big list of company histories on the website.
Many Japanese company histories are included, but some are very much out of date. Nevertheless, it is an interesting place to start when you have struck out everywhere else.