The story of the first volume is quite straight forward. When Aya Mikage and her twin brother turn sixteen, the girl starts having supernatural experiences. Things come to a head as powers awaken within her and cause indiscriminate slaughter while celebrating at her family's ancestral estate. After being rescued by a small household that seems to know more than they let on, it's up to Aya to figure out her new powers and why her family is desperate to kill her before she can do so, all while learning how to adjust to completely new lifestyle. Not helping matters is a mysterious stranger who Aya can't help but fall head over heels for-- which wouldn't be problem if he wasn't employed by the Mikage family to kill her.
CERES, CELESTIAL LEGEND: AYA does an excellent job of setting up the premise, characters, and mystery without giving too much of the plot away. The title character herself is immature, but still quite likable, as Watase perfects the teenage heroine formula that she established in previous works like FUSHIGI YUUGI: THE MYSTERIOUS PLAY. She's an enjoyable character who has no problem charging in and taking control of her own destiny, even if the universe itself seems opposed to her happiness. That doesn't mean that she can't be broken down, as some of the best scenes in the first volume come from her weakest moments. While the character may seem a bit cliched today, especially in comparison to other Watase heroines, she still manages to make a unique identity for herself through her actions.
Speaking of identities, almost everyone introduced in this volume continue to play major roles right up until the end of the series. Supporting characters, like Yuhi and Suzumi, are quickly established with just a few scenes, which is necessary for such a fast paced graphic novel. Furthermore, the story knows how to balance horror and humor without detracting from the tone, as can be expected from a veteran like Watase.
Unlike other magical girl manga, Aya's "heavenly" powers are nothing to desire. Watase pulls no punches in depicting the utter devastation that results from their usage, giving the Mikage family good reason to want Aya dead. People outright die when she loses control. While Ceres herself only appears on the final page of the first volume, it's interesting to see that a character named after the Roman equivalent of Demeter takes on the righteous fury aspects of the mythological character instead of the motherly traits. While it makes complete sense in retrospect, it's an unexpected turn during the first reading that heightens the mystery even more.
Of course, what's a shojo manga without the romance? Toya is an interesting character, as not even he can explain why he acts the way he does; it's clear he's devoted to the Mikage, but something pulls him back to protect Aya anyway. It's no wonder that Aya falls for him: he saves her life several times, and even goes out of his way to try to comfort her later despite his obligations to the Mikage family. Besides, in their defense, they did have most of their moments together before either of them discovered the Mikage's plan. Even so, it's not clear why he personally likes Aya at all. He's pretty much just a pretty face at this point, and the build-up for their future romance is a little too telegraphed for my liking.
While not perfect, the first volume CERES: CELESTRIAL LEGEND is a good introduction to one of the best series within the shojo genre. Highly recommended for anyone that likes good old-fashioned supernatural horror with just a touch of patented Watase-goofiness.