|“||Chastity and grace... Traditional virtues that have been lost. They comprise the educational ideology of Oso Academy. They're priorities that are not valued in boys, only in girls. After having them instilled in us, we're shipped out as a brand-name product —"refined, sheltered maidens"— and purchased by men who seek a classic piece of furniture called "a good wife and mother..." for a formality known as marriage.||”|
Shimotsuki, as a girl, is quite rebellious and critical of the academy. She is sensitive to the "differentness" of Rikako Oryo, feeling a connection with her classmate to whom she speaks about the mysterious Kozaburo Toma. After a friend of hers is murdered on campus, she insists on taking the test of job adaptability to see if she might enter law enforcement as a way to honor her memory. Shimotsuki may be homosexual, though this is never stated outright.
Kirino often sneaks out of school to take photographs. She dislikes the atmosphere of the academy and is afraid of one of its female teachers. As opposed to some other students, she is straight and has a crush on Kozaburo Toma, a boy rescued from Ogishima by her father's human rights organization.
Oryo is the idol of Oso Academy. This enables her a certain freedom which she uses to alter her late father's works of art into gruesome sculptures. She is known to have sexual relationships with her victims.
Okubo's miserable family life and isolation from society by school make her eager to befriend others. Oryo's charming appearance and unique views eventually lead her to her death.
Kawarazaki is a mild-mannered, common girl who is unable to resist peer pressure. Not acute as Shimotsuki, she is also murdered by Oryo.
Using the alias Yukimori Shibata, Makishima successfully infiltrates the academy as an art teacher. It is implied that he is there to observe Rikako Oryo. He is seen to be charismatic and charming with his colleagues and students.
Toma is a person with a strange family history and a resultant twisted view of the world. Despite this, he manages to secure a position at Oso Academy as a teacher of social science. Girls play tricks on him and some crush on him. Later, he becomes a murderer of several school girls, using them to create specimen-like sculptures; these being the very ones investigated in the Specimen Case.
- Due to their isolation from society and adolescent mindset of sexual experimentation, both genuine and situational homosexuality is practiced among the students. A school idol can easily catch some girls' hearts.
- Despite the school's endless efforts to protect their reputation as an elite school, their lack of proper management and precaution has them employing not one, but two murderers as instructors: Makishima and Toma.
- Another name for the school is "Sakurashimo Gakuen" (桜霜学園) which can also be read as おうそうがくえん, meaning "Oso Gakuen."