<p>Effective verbal sexual communication is linked to fulfilling romantic relationships and better sexual health. However, research in Asian contexts, including Japan, remains underrepresented. This study explores how and with whom Japanese youth communicate about sexuality, what topics they feel comfortable discussing, and the limitations they face. Semi-structured interviews (<i>N</i> = 67) were conducted between June 2021 and March 2025 to address these questions. Findings show that sexuality is difficult to discuss openly and depends on peer context. Same-sex groups provide safer spaces for such conversations. Otherwise, topics like <i>ren’ai</i> (romantic love) or <i>oshikatsu</i> (idol fandom) are more frequent and perceived as more enjoyable. Male participants who had never been in a committed relationship often engaged in discussions about sex as “dirty jokes,” myths, or pornography within their same-sex groups. Those behavior was not observed among female participants or participants in committed relationships. Despite general discomfort, gender and sexuality lectures supported more open sexual communication and greater confidence across all genders. Regarding sexual assertiveness in committed relationships, a gender difference was observed: male participants expressed sexual desire both verbally and non-verbally, while female participants often defined sexual consent as saying “no” to undesired sex but difficulties to say ‘yes’ to desired sex. These findings illuminate the challenges of sexual communication in Japan and provide a foundation for future research into whether patterns found in Western contexts apply or diverge culturally.</p>