It isn't really the first problem that pops into anyone's mind but I have found it rather annoying. That is the obvious separation between boys and girls. I'm not even really sure if I can satisfactorily into words what the problem is but I will try.
Girls just don't seem to be...as free as in the US. Sometimes I find myself bored because it just seems like...Japanese girls' number one priority is to sit there and be cute. Boys are so much more at freedom to do what they want and have fun.
When I say that it seems like girls' number one priority I don't mean they don't have ambition but literally it just seems sort of like a "you sit there and look cute while the men go out and do whatever." Japanese boys are CONSTANTLY up to something crazy while the girls sit there saying "KAWAII" about everything. There also isn't such thing as ladies first here. It's men first and the girls just wait their turn (although once a boy cut in from of my at school and his friend pulled him back and said, "ladies first" ......though I don't think this is a normal occurrence between Japanese people.)
Even my friend Matthew, who is from the USA as well and in a nearby city said "If I was a girl I would have gone to Europe, not Japan."
I'm not saying to girls, "don't come, it's horrible", just don't expect the same amount of....I don't know...not freedom, per say, but equality on what's expected of you? It's only a little wearing sometimes but oh well.
Other things I've noticed about Japanese girls and from what my host mother told me is that sometimes, behind the sappy/cutesy facade they are real *******. Me and some of the girls actually ignore each other already. I used to say hi but after they stopped replying I was just sort of like "eh." Especially after a story my host mother told me about my host sister and how she used to be harassed by girls smiling cutely and then saying horrible things.
Everyone is probably thinking I hate Japanese girls but that's not true at all. I have made some great friends, girls and boys, who are so patient with me even if sometimes we can't understand each other.
I don't know if my friends who are girls are the more rebellious type (ie: A few refuse to brush their teeth after lunch and some others refused to join a club, hehe) but they are awesome and I hope we can all stay friends.