Liferay, out of the box, allow Japanese search in components which have support for localization (ie. Web Content).
Unfortunately, with components that don't have localization support, the Search Portlet doesn't work with multi byte languages such as Japanese, Korean and Chinese out of box.
Components without language support
- Message Boards
Add support to Japanese search in components without localization support.
Proof of Concept
Here is a PoC for adding localized indexes for Liferay6.2 + Solr 4.3.1 (or higher version) + Solr4 plugin environment: