Mentaiko is a food which I couldn't bring myself to eat for quite a while after moving to Japan. Its marinated roe of pollock and looks quite gross.
Did manage to try it after a few years and now love it! Although I do need to eat it with rice and still probably couldn't bite one in half ^^;
Another Japanese dish I cant eat is Natto - its that sticky gooey fermented beans thing which you can see in action below. Are there particular Japanese foods which dont agree with you?