Visually I would say that walking through a busy street looking for a client's office and coming upon a small hidden away serene temple is one of those thing that really strikes me as completely Japanese. Another one is getting up from the subway into the busy nightlife area of Shinjuku at night, seeing all the neon signs and the complete mix of people stumbling around the street. These things are something you could never experience anywhere outside Japan.
Audially I think it's a tie between all the female robot voices talking to you in Japanese from every machine and the busy noise in a Japanese izakaya of people screaming orders, laughing and the general happy noise. You could would never experience this anywhere outside Japan.
|Something like this, if all the men were drunk on cheap liqour|
So if you come to Japan and want to have an unique experience, take a late train on a weekend, heading out from the city towards the suburbs and make sure that you are completely sober for the full experience!