Age of consent in Japan is 13. No, really.
As for attitudes about sex, that's...a very interesting topic. My Japanese teacher in school actually went on a little about this recently, apparently the people there would rather do it on a bench in a park at night than at home, which might sound downright exhibitionist if you didn't take into account that in some areas of Japan, the houses are so tightly packed that even if you manage to get your own home (with the rather expensive land costs), that kind of activity at home would bother the neighbors because the houses are that close.
Interestingly, despite the common fan-service in many anime/manga, public displays of affection are frowned upon in that part of the world as well.
I'm not going to call myself an expert on the Japanese, though. I mean, I've never been to Japan.
I'll agree with that.