Problem
I copy-pasted some Japanese text into the WordPress editor and it shows as ????. On another server, pasting the same japanese text shows the japanese text on the page. No plugins seem to be affecting this. Something with the server or WordPress configuration must be affecting displaying the foreign characters.
Solution
The problem was caused by using the Fantastico automatic install from the cpanel. When Fantastico installs wordpress all the fields in the database have a data type of “latin1_swedish_ci”. Using this data type, characters like Japanese and Chinese are not supported. You’ll need to change the data type of the fields to “utf8_general_ci”. I changed post_title, post_content, and post_excerpt fields in wp_posts and it seems to be enough. It depends how much you will have foreign characters though, you may have to change more fields. More info can be found in the source below.
Source: http://wordpress.org/support/topic/special-characters-converted-to-question-marks-on-save
keywords: wordpress not saving japanese characters