I am translating geonetwork into Japanese now.
I input metadata in Japanese and confirmed that it was displayed in Japanese after save
definitely. Japanese data are stored in UTF-8 in a database.
However, I cannot search metadata in Japanese.
I had the same problem with french characters...
To problem is in the tomcat config files.
By default, tomcat will make all http request (like searching) into iso-8859-1.
So you need to specify tomcat to do it in utf-8
add this parameter --- URIEncoding="UTF-8" ----
to your <connector ....... /> tag