It has to be said but unfortunately Tokyo is probably one of the world’s least accessible cities. Getting around involves extensive use of the train system and most stations are ill equipped.
Elevators and escalators are few and far between, ticket barriers are narrow, platforms are crowded and the people fast-moving.
However, on a brighter note the Japanese Red Cross Language Service runs a very good scheme. They offer advice on where to stay; they can meet you at the airport and show you the sights.
They also have a website which contains useful information for disabled travelers: http://accessible.jp.org/tokyo/en/