Well as Shinto does not "Sin" your correct, but there is a duty to have sex so many times - there were several relgious hook up areas in Japan to fulfill your religious duty. Its one reason that love hotels are so common as well in Japan as until 1945 sex had rules but it was considered a positive.
However maybe the Japanese girls who instructed me where just playing me to get me into bed. I certainly had made up tall tales about Canada and our pet Polar Bears - its a fun game to push the limits on other cultures (as long as you fess up in the end of course but not everyone does)
example: (The National Snow House)