Cyrillic is the script used to write Russian and some other Slavic languages (named in honour of Saint Cyril, whose followers invented it). It looks like this:
I believe there is an alternative Russian firmware you can flash to the 650 which would enable it to support Cyrillic script. Though I'm not sure why you would need this to learn Japanese... Unless you are a Russian speaker and would prefer to read a Japanese textbook in Russian.