Before I visit Japan, I downloaded 2 applications on my phone.
Both are navigation for rail way.
Trains and Subways are all over on central Tokyo and it’s easy to be lost.
(Buses are also one option but we didn’t use local buses.)
It tells you which station exit you need to use and how to change trains.
(Even same station, sometimes you need to walk long way. (・´з`・)）
I also used it to make plan for next day.
It estimates how long it takes to get to your destination.
Reason why I downloaded 2 application is that sometimes it depends on application,
result are soooo different.
So I checked both results at beginning but I used Navitime mainly after all
because its suggestion was always a shorter time .
I used this Japanese ver.
Its has GPS function as well.
NAVITIME Transit in many languages.
(Support 12 Areas and 11 languages)
NAVITIME for Japan Travel
There are premium versions for each app but free version was enough for me.