I have a hunch it's the same with Japan (part 1 of this).

House prices in attractive areas (in and around Tokyo) have increased drastically over the last few years.

Meanwhile, houses in the countryside are on the market for almost (and often literally) nothing.

I guess the question is what the data is actually measuring. would still expect the graphs to show an increase if they measure the price of actually sold property.

Just checked OECD data and to me it looks like prices are rising in similar ways in Germany and the US since 2015. Japan does in fact seem less steep but it's still rising, not flat as the graphs on TFA would suggest: https://data.oecd.org/chart/6ztU