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...
Adapted from a 2011 novel by author Mahokaru Numata, Yurigokoro has Ryosuke's father, who is stricken with advanced cancer, as a man with a diary. When the family discovers the father's diary in the latter's office leafing through it reveals notes written by a murderer. Are these fictional accounts or the memoirs of the diary's owner?