On their 16th birthday happy-go-lucky Aya and her twin brother Aki are ordered to their grandfather's house, where the entire Mikage clan has gathered - but events take a gruesome turn.
Seeing her father's destruction unleashes a power within Aya: she is rescued by Toya, Yuhi and his sister-in-law Suzumi. But what they have to tell her is not well-received.
Refusing to believe Suzumi's story, Aya returns home, then goes to the hospital where Aki is recovering. Her mother confronts her there over her father's death. Meanwhile, Toya is ordered to keep her safe.
Celestial being Ceres finally awakens with a disturbing truth about why the Mikage want Aya dead. Later, Yuuhi is preoccupied by his feelings, while Aki has some ethereal issues to work out..
Toya brings Aki to the Aogiri house, and though it pleases Aya, it is less than pleasing to Ceres. Why? Perhaps because of the scars he suffered during his awakening on the night of the twins' birthday.
Still lost, with no clear path forward, Aya follows Toya in hopes of finding answers. Instead, Kagami forces her into a locked room so that he can have a little chat with Ceres.
Drawn to another girl at her school, Aya makes a new friend. However, it turns out that the new girl's burning passion for her forbidden love is all too literal, as the first test for Kagami's C-Project is already underway.
Suzumi and Yuuhi deal with family issues, while Aya tries to deal with her own warring heart. The Mikage, however, aren't content to wait, and the C-Project sets its sights on a new test subject.
The Mikage attempt to brainwash Suzumi, and it's up to Yuuhi and Aya to save her. However, protecting her from physical harm is only half the problem. Meanwhile, Aki's problems are just beginning.
A young girl appears at the Aogiri house and asks for a favor--from Ceres. While it seems innocent enough, the circumstances around that favor land Aya in the middle of yet another C-Project experiment.
Though the C-Project experiment is a success-in some ways-that success is short-lived, and so are most of the subjects. Meanwhile, Aki is having trouble telling his present from his past.
Toya makes the decision to abandon his past, even as the past takes control over Aki. The two fight to escape the Mikage tower, but only one of them will leave.
Aya makes her choices, both between the two men competing for her, and with how to deal with Aki and Ceres. Meanwhile, Aki is taken beneath the Mikage mansion in order to meet his destiny.
The longer he's close to Aya, the more vulnerable Toya is, and he is painfully aware that something must change. Could his memories hold the key? Meanwhile, Aki is busy tracking down Ceres, which leads to a violent showdown.
The hunt is on for Ceres' legendary robe, bringing Aya and company all the way to the sea. Once there, Toya discovers some long-buried memories, including a girl who looks strangely like Aya.
The C-Project moves into its final phases, and Aki does his part by capturing Aya. Meanwhile, Toya finds his reason to love, and races back to Aya's side in order to pull her from the Mikage's clutches.
To escape the Mikage, Aya and Toya escape back to the coast, and assume what they hope to be a normal life with one another. However, they can't escape their past, particularly not the forgotten memory they both share.
Since they can't have Ceres, the Mikage kidnap Chidori and her brother. Toya and Yuuhi go after her with the help of the Aogiri family, but the results are anything but happy.
When their attempted rescue ends in shambles, Aya addresses the Mikage themselves to find out where Toya is. But the news she learns from them is nothing less than heartbreaking.
Ceres learns of the ultimate goal of the C-Project, and witnesses the fruits of its labors--and hers. Then, she reveals the truth behind the myth of the hagaromo legend, and why it isn't as clear as it might seem.
Toya's memories have finally returned, along with the knowledge of everything he is. With the collapse of the C-Project, and the Kagami in disarray, Toya and Yuuhi must rescue Aya-and reunite Ceres with the hagaromo.
