The Maps app in Windows 10 Mobile TP has much better support for Japan than WP8 did in the past.
However, there are some important points missing which I want to mention:
- Lack of public transport data for directions, particularly buses (at the very least, the popular bus companies in and around Tokyo - Kanachu, Keisei, etc must be covered)
- Even in cases where public transport data does exist (e.g. for major train lines), some very strange routes are being suggested depending on exactly how the start/end locations are written
- Searching for locations by address is hit and miss. It seems search is only being done on the location name and not the underlying address. This is primarily when searching for addresses entered in Japanese language - search in English doesn't work except for the most major place names). Search does not find some names of buildings etc even when they can be seen on the map itself
Hoping to see some improvements in these areas as it will then be a very useful app.