For Party

What brings you to Japan?

Vacation

I'm here for vacation.
When did you arrive?/When did you get here?

A couple nights ago.
When do you leave?/When are you leaving?
Are you enjouying your time in Japan?/have you enjoyed your time in Japan?
Where have you been?
You should go to...

Business

I'm here on business.
What  do you do for work?
Do you come to Japan often?
Did you have time to sightsee?
You should go to... 
A little bit. I went to the Tokyo Tower.
Did you know they have the Sky Tree now?
It's a new tower on the east side.