Ask to see the auction sheet, and don't take any excuses from them, they keep those on file and if they won't show you, then I would conclude they are hiding something.
When you get the auction sheet, make sure the numbers match the vehicle you are looking at, sometimes they'll give you one for another vehicle and since its in japanese, hope you won't notice but the numbers don't lie. If you don't know how to decipher the auction sheet, google around and you'll find the info showing what each letter and number means.
Also, not critical and most often not available but will help you make a decision, ask if it has logbooks and if the odometer reading has been certified.
Apart from that, do the usual checking.