They do appear to have a japanese checkout screen - I've been getting orders from japan but often the paypal email and online info is not readable - its obviously entered by the buyer in Japanese, which paypal just lists as square boxes.
I often have to email and get the buyers to resend their info in English. It seems like the Japanese interface isn't fully functional.
Edit - OK I get it now, the boxes are just because I didn't have the east asian languages installed on my pc, but still I'm not sure that Australia Post will cope if I just print the Japanese script to put on the parcels.
Anyone know if I can post items from Aus to Japan with only Japanese script on the address?