Tokyo was awesome and I want to go back.
I spent a week at the "Anne Hostel" in Ryogoku area and met lots of travelers from all over the world. I think it had the highest diversity of people from different places compared to other places where they seem to all be Australian(Nicaragua) or Argentinian (Colombia).
I highly recommend visiting the Tokyo Government Building which has 48 floors and a huge viewing area with lots of different vantage points for guests. Apparently on a clear day you can see Mt. Fuji ( 
Surprisingly there are tons of parks scattered everywhere in Tokyo. I like this because while you're in a major city, you have immediate access to wildlife, greenery and Japanese landscape architecture which is amazing. I think I love their use of bridges the most.
My favorite building in japan is definitely the "Tokyo Skytree", while I didn't have a chance to go to the top, I had a nice time trying to take pictures of it. It is over 2000 feet high and was the tallest structure in the world in 2011.
Beyond all the sights, I generally enjoyed just wandering around Tokyo as it was very clean, orderly and everything seemed to work intuitively. I can't read japanese, but most of the time signage had an easy to follow sign.
Japan has a lot of alley ways that feel like their own little universe. The best example I have of this is Golden Gai which is a district w tons of tiny little restaurants and it looks "just like in the movies".
When I went with my group we crawled to the upstairs section where about 15 people were crammed in a few hundred and got some Soba.
I'd love to go back to Tokyo and be able to spend more time, also really want to go to other cities such as Kyoto, Osaka, and Hiroshima/Nagasaki.
Bonus picture of drunk guy from Belarus passed out in the hostel lounge. 
ahhh you should have gone up to the top of skytree! the sight is amazing ahahha
A reason for me to go back! I feel like I had just a sneak peak of Japan. I will do much more exploring next time.