Tokyo is a giant city with more than 10 million inhabitants. If you’re going to Japan, don’t miss out the nation’s capital and in my own opinion the 2nd best city in the country (I like Osaka best). Tokyo is huge and there’s lots to explore - it’s so big that a separate guide can be written for each neighborhood. You could easily spend 2 weeks in Tokyo alone. There are also many possible day trips to be had from Tokyo.