yea bro the place is sick as hell i lived there for about 7 months working,
few questions,
1) where about in japan are you going (which islands and shit)
2)How much cash you got for spending.
3) how much time have you got.
4) what type of shit do you wanna see (pubs clubs, culture, random fun shit, huge partys)
a couple of things you gotta do while you are there without exception,
go see a sumo show they are fun as hell watching huge guys takle each other, also really a good look into thier culture.
buy beer out of a vending machine.
eat whatever they give you as long as its not this shit called Nato (fermented rice cake thing pretty nasty.)
and just walk around and talk to random people they are amazingly friendly people i have been invited to dinner but so many familys who i met that day they are really chill people. get used to old fat dudes reading hardcore porn on the train.
oh and dont put your chopsticks down in the rice and leave them there its something about death, i learnt the hard way.