Age-specific incidence rates of breast cancer among Japanese women recently increased in a bimodal distribution pattern with two peaks in the premenopausal and postmenopausal groups. The recent incidence rates among premenopausal women in Japan appear to have exceed those in the United States. Focusing on diet in Japan during 2005 through 2015, changes in the incidence rates of breast cancer, different from those of colon cancer which is originally regarded to be increased by westernized lifestyle factors, negatively correlated with the intake of fruits, vegetables, algae, or fish and shellfish, whereas those positively correlated with the meat intake. The continuing increase in breast cancer incidence among Japanese women was associated with the recent change in food intake from the Japanese diet to the Western-like diet, especially among premenopausal women. From the relevant literature, the changes in food intake among Japanese women are inferred to possibly link with an increase in inflammation and estrogen levels.