As research on the impact of sexuality on various demographic outcomes continues to grow, it is important to examine the complex intersections of sexual orientation identity, sexual/romantic attraction, and sexual behavior. However, most of the previous studies on these topics use data from Western countries that have particular histories of sexuality, limiting the generalizability of their findings beyond Western societies. We describe dimensions of sexuality in Japan, where historically no religious authority has condemned same-sex behavior and legal prohibitions against same-sex relations existed for only a decade in the late nineteenth century. We conduct a descriptive analysis using data from the 2023 “National Survey of Family, Gender/Sexuality, and Diversity,” the first nationally representative survey with detailed questions about multiple aspects of sexuality in Japan. We highlight three key findings. First, among the respondents who selected “don’t want to decide, haven’t decided”—a category originally created for queer/questioning respondents—as their sexual orientation, the proportion of those who indicated exclusive heterosexuality as measured by any of the indicators of sexual orientation, such as sexual attraction, romantic attraction, and sexual behavior, is higher than expected. This raises the possibility that some heterosexual respondents may have mistakenly chosen this category. Second, the proportion of people reporting same-sex sexuality in all three dimensions of sexuality (same-sex attraction, same-sex behavior, and same-sex sexual orientation identity) is low, particularly among women. Finally, the prevalence of asexual populations differs by whether sexual orientation identity or sexual/romantic attraction is used to capture this population. Our analysis extends the demography of sexuality by examining unique non-Western data and putting in context the previous findings observed in Western countries.