How are foreigners in Japan treated?

Question:

I'm 1/2 Black and 1/2 Asian. I hear people with darker skin are treated differently, but if that's so, why is Manba/Ganguro a huge trend? How would I be treated?
Only answers from people who have been to Japan as a foreigner, someone who knows a person who's been to japan as a foreigner, or someone who lives in Japan please. I'm not looking for answers from people who are just saying things based off what they hear -__-

Answer:

I am British have a Japanese wife and have spent a lot of time in Japan over the last 11 years. People in Japan keep themselves to themselves unless you make a first move. Even if it only consists of a 'konichiwa', a smile or a nod. Then they'll generally be friendly in return. A city is also different from a village or one of the tiny islands where I've spent most time. A village is more friendly than a city, as with anywhere.
As to mixed race. One of my wife's friends in Tokyo. Her daughter has seen a lot of me over the years (she's 7 or 8 now) so she's maybe used to foreigners more than other kids. When a child started at their school 1/2 Black and 1/2 Asian, no-one except the friend's daughter wanted to partner them in a school thing. Which did seem rather mean to us and my wife's friend.
As children they were probably unsure of things which weren't the same as usual.

All I can say if you are going to visit Japan is be friendly to people (and show them respect), even if they don't initially seem friendly to you, and they will be friendly back.