What did ordinary people really eat in premodern Japan, beyond the dishes described in cookbooks and the bones discarded at urban waste pits? Reconstructing past diets at the level of individual food items is remarkably difficult. Traditional archaeological approaches and stable isotope analysis of human skeletons reveal broad dietary categories—such as reliance on marine fish and C3 plants. But they cannot show which specific taxa or tissues each person consumed, nor how access differed among social groups in a stratified society like premodern Japan.