One way to determine which are which is to try converting from one character encoding to another... For instance... pick a unicode character... if you can convert it to EUC-JP or Shift-JIS or ISO-2022-JP, then it's a valid japanese character. If you can't, then it's not. Do this for all unicode characters, and voila!

For unicode, this appears to be (allowing for gaps of 255 chars at most):

• 0001 045F
• 2010 2312
• 2500 266F
• 3000 30FE
• 4E00 9FA5
• E000 E757
• FF01 FFE5