Android Auto has been available in a handful of countries since it launched last year - after being announced at Google I/O 2014. However, one country it wasn't available in was Japan. That was until today. Google announced at a press conference this morning that they were making Android Auto available immediately in the country in a select number of models. These models include the 2017 Audi Q7, Audi A4, the 2016 Honda Accord lineup, and a few other models from Maserati and Volkswagen. There are also some third-party head units available from Nissan and Panasonic that support Android Auto. At Google I/O 2016 in May, Google announced that Android Auto would be coming to all smartphones and tablets as a standalone app. So if you're not in the market for a new car, and don't want to buy a new head unit, the app should be available in the next few months for everyone in countries where Android Auto is already supported.
During the press conference, Google also talked about local app support like music streaming service Awa, which is popular in Japan. WeChat is also supported, but Line unfortunately isn't. And in Japan, Line is much more popular than WeChat is, currently. The Android Auto software that's available in the Japanese market now, is the same as what we've been taking a look at here in the US. The major difference is the supported languages, which is determined by your phone (i.e. if your phone is in English, then Android Auto will be). Otherwise, there's nothing all that special about Android Auto in Japan.
Two of the bigger car makers, Toyota and Mazda who both call Japan "home", still have not gotten on board the Android Auto train. Toyota has said before that they are content with their own infotainment system, and don't want to "give Google the keys" to their vehicles. Ford felt the same way, but eventually came around, announcing Android Auto support for a number of their vehicles earlier this year.
With today's announcement, Google finally joins Apple in bringing their vehicle OS to Japan. As Apple CarPlay has already been available in Japan for quite some time. The Japanese market is a pretty big one for Android Auto, as it is a huge automobile market overall.