Nipponica

The government will introduce a new preclearance system from next January, starting with tourists from Taiwan, NHK reported. Visitors will be able to complete most of their immigration screening before departure to help shorten the time taken for entry procedures on arrival, according to the report.

There are not much details on how this will function, but I doubt it will mean that Japanese immigration officers will be deployed to foreign airports like the US version of this program. I assume it will just be a more rigorous check of paperwork and perhaps receiving your passport visa sticker before boarding. Perhaps using automated immigration gates in foreign airports?