there is absolutely no way for fast to show whether the kms are genuine. you have as much chance of finding that info from one of those ebay workshop manuals, or even a piece of gum on your shoe, as FAST is simply a program that has all the data for the different models of cars in it which you can use to find part numbers.
as for how to find out how many kms the car has really, that is pretty hard to do. firstly you would need to find out how many kms the car had in japan (import papers would be a start, but that doesn't help if the odometer was changed before being imported). then you would need to find out if the odometer was changed, and if it was, how many kms it had done when it was changed and how many kms were on the new clock that was put in there.