In case it's gone by the time you go there, this is the link to the Avatar entry.
The series is about preteens and teenagers growing up in an alternate world. The usual adventure manga prototypes and props are there, but the creators use them to good effect, and the series is captivating.
The entire first two seasons are available on the Internet free of charge or registration, but not on YouTube. There is no way that the powers that be cannot be aware of its cyberexistence, since it's easy to find. I think that the content owners have a finely calibrated IP protection policy where they let the small fry do their thing while coming down hard on institutional threats like YouTube (or Yahoo, if the Avatar found its way there.)