Call the Japan HIV Center AIDS Hotline for AIDS information and test center information in your area:

NOTE: Tests sites in Japan do not always have staff who can speak English, so it's a good idea to take someone along with you who can speak enough Japanese, if you don't already, to translate. If you don't speak Japanese, call the numbers listed for directions to the nearest subway "ichiban chikai eki wa nan desu ka?" (Which is the nearest station?), and from that station you can ask people "Hokenjo wa doko desu ka?" (Where is the health center?)