Despite the myth of ethnic and racial homogeneity, the population of Japan has been and is increasingly becoming diverse. Among these diverse population are those so called hāfu, mixed Japanese born to a Japanese and a foreign parent. The narrow conception of Japaneseness often leaves mixed Japanese to be excluded from Japanese society and question their claims to being Japanese. This chapter provides a historical overview and transformation on how individuals labelled as “mixed” were treated socially and politically in Japan before 1945 and up to the present. We also present a brief state-of-the-art of the emerging field of hāfu studies and suggest the future direction of this field.