I am not too sure why it would have installed in Japanese. You can however try installing English. (By the Settings → Language tab)

Did you mean this?

It was about the sections like the support tab that are drawn from the web, and were based on IP, not windows language, so could show different languages depending. Thinking about it now however, I remember reading that this may have changed, and is not relevant anymore.
Aside from that, it seems unrelated to the issue mentioned here, so can be disregarded. Sorry for any confusion.