The purpose of this study was to describe and explain Japanese health and physical education teachers' experiences teaching sexuality education at the high school level. This qualitative study used the interview method, with an in-depth, semi-structured approach. The research sites were Japanese high schools located in the Kanto region of Japan. Participants included eight health and physical education teachers who taught sexuality education at the time of this study. A constant comparative analysis method was used to interpret the data, with three themes emerging from the data: (a) "teaching how to avoid unwanted and unexpected pregnancy," (b) "be careful about sexual comments and terms that could turn to harassment," and (c) "use instructional resources that help students' transformative learning." Findings suggest that health and physical education teachers must be highly ethical professionals, whose attitudes and actions are focused on what is best for their students while teaching sexuality education. To advance the quality of sexuality education instruction, teachers, administrators, and researchers need clear and focused goals related to the status, quality, and relevance of sexuality education programs and curricula.