I think your issue will be solved if you:
1. Log out.
2. Go to the Log-In screen and switch the language setting on the top right from English -> Japanese.
3. Continue registration on the Japanese website.
If you're having trouble doing registration in the Japanese website, you can Google Chrome to translate the entire page so you know what you're filling in (nickname, password, etc). This is what I used when and it made registration very easy.