For US Passport holders, Japan just requires a passport. For China, you need a visa - an expensive one. The Chinese Consulate is located at 1 East Erie St, 5th Floor. It's $130, and requires you to have a photo, a filled out passport form, hotel and airline reservations. It takes about a week to get back. I've been to the consulate a few times, and it's hit or miss on service.
So c'mon - use that tax refund and head to Asia.