First off, the G rating means that story is safe to read to little children, and that there are no swear words. They are clean.
A PG rating means that there may be some adult language used in the story, or maybe the chars get into some heavy situations. No sex though. Safe for about 11 and up.
A PG 13 rating is exactly what it says. You gotta be around 13 or more to read this. If you're mature enough, go ahead and read, but I don't want to hear about it. Definately swear words, and maybe a little fondeling. No drastic details.
NC 17 is full on. Swear words, details, death, gore, blood...anything our dirty little minds could come up with. I don't want to hear about how your fragile little mind has been warped after reading one...so...beware. Anyone who dares can read em. I reccomend around 14 or 15.
Now, for your day lesson in Japanese. I'm not going to sit there and make every jap word a link that you can click on to see a defintion, so, deal with it.
This will simply be a link to a much better Jap dictionary. Okay? Now, click here.