i have a 15 days tourist visa here in japan and i want to apply a Chinese tourist visa here

It’s possible for you to get it from there. Just have a try! You need to prepare those documents: your passport and copy of its data page, the filled-out application form, a passport-sized color photo, your valid entry permit for Japan, and proof of transportation and accommodation arrangement. After, submit the application to the embassy of PRC to apply for it.