This small extension can localize & configure Magento default wysiwyg editor.
Magento already has built-in TinyMCE a Wysiwyg editor, but it can only use English and cannot customize without edition Magento core codes.
This extension aims to localize it into Japanse (or you can install other TinyMCE locale manually) and site owners can edit TinyMCE configuration via Magento admin panel.
And one more important thing, this extension automatically load one additional CSS file for TinyMCE editing area. Its file name is "adminhtml/default/default/celticmce/editor.css". By default, it is empty. You can edit it by yourself.