This chapter provides a general overview of intercultural (international) relationships and marriages in Japan and reviews existing research available on mental health and well-being of the foreign wives married to Japanese men. We also include our own analysis of the “Survey of Foreign Nationals on Life and Work” conducted in 2018. Previous studies have emphasized the difficulties and problems of marital relations; however, our data show that marriage to a Japanese person, if anything, promotes, or at least does not worsen, the social inclusion of immigrants and their subjective well-being and mental health. There is still limited research on mental health of internationally married couples in Japan, and there is a need for further research that holistically examines individual characteristics and their impact on the sense of belonging, mental health, and well-being.