Sexual customs in Japan
Although there is no verification method, Japan as if it was "extra" as for something about SEX from ancient times. Surely the "sex industry" is also fulfilling, but ...
For example, the system of Concubine system of "Oku" in the Edo era, I usually feel that it is impossible for other countries to do such a thing.
I think that I would like to explain about sexual practices that seems like "Is this unique to Japan?"