Metro and subway operators logos
The app is perfect and relied on it heavily during my visit to Japan. It was my main reference to get around the cities and places in Japan and I recommend travellers to use it. The only suggestion I would like you to add to the app is metro/subway operators logos to make it easier to distinguish between the different metro operators. Mentioning the lines names only is good but not enough especially for a tourist who is visiting Japan for the first time.