They throw stones at them. and they have to give up their seat on the subway to a japanese man if they ask for it!
Very much like America before they got their rights as human beings.
I'm African-American and spent a week in Japan in 2003 and was treated quite well during my painfully brief stay. I went to a lot of places, daytime and nighttime and never had a lick of trouble. I was just another gaijin gawking at the sights, something I don't deny!