Wonderful! One of the greatest places on Earth you could visit. Lovely country.
My advice would be to learn a few polite phrases in Japanese if you don't know them already. "Sumimasen" = "Excuse me; pardon me" is very helpful. Use it if you are looking for directions or if you accidentally bump into someone on the subway or any other similar situation.
My first time visiting Tokyo, I had almost no Japanese and I still found it extremely easy to get around and enjoy things. Most restaurants have picture menus and there is a lot of English on signs and such but it's still respectful to show that you are willing to learn a few simple phrases. "Arigatou" = "Thank you", etc.
I see you are flying into Narita. Are you staying in Tokyo itself? It's easy to get from the airport to the city by train.