What visa are you hold now in China? is it an L for tourist? or else? to apply in Japan is possible, but you are required to provide your registration card/entry record to Japan when submit your visa application to the embassy or consulate over the area you stay. The other documents are original passport, application form A and B with photo stuck on it. And if they don't accept your Z visa application, you can get it processed in HK from Commissioner's Office of China Foreign Affairs.