Ceres is one of Watase's most popular works and, in my opinion, her best. It's a much more mature story than her others, dealing with themes of sexuality and violence (often a mixture of the two), but as my mother would say, it is tastefully done. Probably 16+ should read this, not because of content, but because the themes are very complex and require a more mature understanding of sex and violence. Besides the 'parental disclaimers,' Ceres is a beautiful love story and a sci-fi/horror thriller with social commentary and humor. The main storyline is that Aya, on her sixteenth birthday, is possessed bya spirit named Ceres. To make matters worse, her family wants to kill her to keep Ceres from being unleashed. So Aya must find a way to rid herself of Ceres...or at least that's how the story starts. There are fourteen volumes in all, so the story has time to become really complex (but not like Pirates of the Carribean 3-I-have-no-idea-what-is-going-on-complex). It's a long series, but it's worth the time (and money if you buy all the volumes like me).