Philosopher Michael Foucault has written that sexuality is the most useful tool in any power relationship. It is adaptable to the greatest number of maneuvers and is capable of serving as support for the most varied strategies. As such it has long been used by most governments in their efforts to stay on top.
Laws pertaining to sexual matters are commonly rife, as sexual knowledge is denied or pushed according to the needs of the state. The means are usually normalization, medicalization and pedagogy. These are modulated by complicated exchanges among governmental agencies, the media and other interested parties.
This, true as it is now, was not always so in Japan. The pre-Meiji years are distinguished by few governmental inquiries into sexuality as such. Sexual practices, habits and beliefs were, in a way, tolerated. It was not, however, that the Tokugawa government purposely pursued such a benign course. Rather, sexual matters were perhaps regarded as too mundane to serve as a governmental tool.