According to Department of Transport in South Australia:

'If you are a VISITOR to South Australia then you are able to drive on the basis of your overseas driver's license, for as long as you can be classed as a visitor, and as long as your license remains current. If the license is not written in English, then you must also have an International Driving Permit (issued from the country of origin), or an English translation of the license, to carry with your driver's license whilst driving. If you obtain PERMANENT RESIDENCY during your stay, you must then obtain a South Australian license within three months of becoming a resident.'

What this means is that all a Japanese person needs to drive in South Australia is their valid license and an English translation. Being on a work visa does not classify you as a resident but as a visitor, and therefore does not require you to obtain a local license. If Australian law recognises Japan's authority on driver's licenses, why can't Japanese law recognise Australia's authority?