The custom of yobai has been deeply rooted in Japanese culture since ancient times, with records dating back to the Man'yoshu, making it a ritual with a long history. This ceremony carries the significance of a rite of passage and, while varying in unique ways by region, holds important social and cultural meaning. It has a strong aspect as a sexual tradition, and its transmission has never ceased. As a local folk practice closely tied to people's daily lives, it plays a crucial role in maintaining communal order. Those who break its rules face severe punishment, such as social ostracism, demonstrating the immense weight of this tradition. Furthermore, due to its high level of secrecy, each region maintains its own distinct rules and rituals, resulting in limited outside contact and the formation of a compartmentalized social structure.