[Bloomzy]

That is such an immense question to ask. Different fashion applies to different parts of Japan and so on...

Work related attire is very much like that worn by 'white collar' workers, so suits etc. When out with friends it depends on where you are going, who is going to be there, but of course as it is in Western countries you are not expected to be so formal.

The Japanese people will understand that you are new to their culture and the majority of people are kind enough to realise that as a 'foreigner' you will not know everything. So the best advice I can give you is to ask people, they will appreciate that you respect them enough to ask ^_^