Japan trip - 1st timer suggestions or advice

[popfed]

I am visiting a friend in Japan in November.

So far I know the "safehouse" is Nagoya and the places of interests are: Tokyo, Hiroshima, Osaka/Kyoto, then Toyama.

My friend is advising on some places but they are relatively new resident themselves.

Anyone who's been got any suggestions or general tips about Japan?

My learnt tips so far:
* apparently slouching and leaning against wall is a big foo-pah
* they aren't into sugar and milk as much as Western Hemisphere