If you feel you want to marry a Japanese lady, go for it. I thought I would never get to meet a Japanese lady so I settled for a American lady. Boy was I sorry. After my divorce I moved to Japan and met many nice Japanese ladies and married my wife.
Most of your problem is self confidence. You must be confident to impress Japanese women. Japanese men are too shy and they like confidence.
Being black means nothing. Not all women like black men, but not all women like white, Mexican, Polish, etc...... The only problem you might run into is if her parents don't want you to marry her and she won't date you if she is sure this will happen. A black friend of mine is married to a Japanese lady here and in Japan, one of the best "ladies man" I knew was black. So don't use this as an excuse to chicken out.
Follow your dream, it usually is right.
