A bit of a timeline to provide context (hopefully enough):
My Japanese wife was living in her Japanese apartment in Tokyo until 2009. This was her main residence with her brother (co-owner) came to Australia and soon attained permanent residence. We rented homes in Australia until we bought our first home together in 2017 and have lived ever since. Her brother remained there and she/they did not derive an income from it - was never rented out. She and her brother then sold the apartment last year and the capital gain was something like $400000. She has payed some tax already according to Japanese tax laws but now it is CGT's turn.
I am wondering if she can call this apartment her main residence until 2017 when she bought the apartment with me in Australia. In which case I'm guessing the apartment would be exempt from CGT between 2009 and 2017. Or, as she became a permanent resident in Australia she automatically revoked the same 'main residence' status, and her rentals with me in Australia became her defacto main residence from 2009? She was paying local rates etc in Japan but not sure if that is meaningful at all. I have also reviewed.thr following webpage but not sure it's relevance, does it only apply for example Australians who moved around Australia?