A murder mystery following six pretty JK, who all have something to hide. The film's Japanese title literally translates to "pitch black girls", highlighting the characters personalities which soon become dark. One day, pupil Itsumi Shiraishi dies at the Seibo Maria Girls High School. The daughter of the school's administrator, Itsumi was envied by all the students there. Surrounding her death is a shroud of mystery; did Itsumi kill herself, was she killed accidentally or intentionally? At the time of her death, she held a lily of the valley flower in her hand. A rumour spreads that someone in the school's literature club, which Itsumi had presided, killed Itsumi...
In the land of Iolph, all the people stop aging in their mid-teens and can live for hundreds of years. One resident, Maquia, feels lonely despite the peaceful and idyllic land she lives in. But one day, the Mesarte army invades Iolph, seeking the peoples' blood for their immortality. Maquia manages to escape the destruction and chaos of war, but with no home or people, she becomes a wanderer in a dark forest. She comes across Erial, an infant mortal boy who has lost his parents, and becomes his guardian. The story follows the relationship that evolves between the two as Erial grows up while Maquia does not.