If you are writing Japanese text in the forum, then you can enclose this text in special tags which will render the text in a better and bigger font. For this there is ja tag:
Example with tags: 英語が話せますか?
Example without tags: 英語が話せますか?
In the post editor, you will find buttons for the tag.
Edit by moderator:
If you need to find how to install Japanese characters on your system, please follow this link to a comprehensive guide on Wikipedia.