Depending on the year japanese cars don't have a vin, only a chassis number. If your car was brought in under the 15 year rule it almost certainly wont have a vin.
More recent imports are assigned a vin by DOTARS when you get import approval - it is based on the chassis number with some extra crap added to it. I dont know about earlier imports.
In SA you need to have a plate stamped with the VIN number and attached to the chassis/firewall.