Foods from other cuisines are eaten too, but the above 3 are the main ones by far, especially at home. You can see that reflected in all meals. When the cook of the family (usually the mother or grandmother, but these days some men are taking on the role of primary cook of the house too) is deciding what to make, s/he usually starts with what the main starch will be: plain steamed rice, bread, Japanese or Chinese style noodles, fried rice, etc.
A typical breakfast is usually Japanese style or Western style - or 'gohan-shoku' (rice based meal) or 'pan-shoku' (bread based meal). Cereal is sold in Japan but isn't that popular, and only a few varieties are available.