In both cases you need a local presence to register Chinese or Japanese domains. We had a recent discussion about Chinese Domains here [webmasterworld.com] a while ago but the information is still current.
I am not too sure about the specific restrictions in Japan. Perhaps Bill, out resident Japanese expert, will come along soon and help you out.
There is a lot of discussion about the Asia-Pacific region in general at the Asia-Pacific Forum [webmasterworld.com] which I think you will find interesting. Do join in.
Onya
Woz
Technically anyone can register a .jp name now. There is a very good FAQ in English here [japanregistry.com]. If, however, you want a .co.jp name then there are some fairly stringent and archaic rules you need to abide by...they limit you to one name per registered company, and those names cannot be sold or transferred.