Best city in the world
In Tokyo everything functions perfectly and everything is clean. People are extremely considerate here so you better mimick their behaviour asap. It's a capitalists paradise you can buy anything you want, everywhere and even things you didn't even thing that existed. There isn't much to sightsee except some parks and maybe museums if you like that. You just watch the city and go shopping or dining here. You need at least 5 full days here, don't even bother with less.
Insider Tip:COME WITH AN EMTPY SUITCASE. You will regret if you don't have enough space to bring home stuff. Also get an "IC" card (Suica or passmo) it will save you a lot of time and trouble.