バイブルブラック 外伝
Overview
Twelve years before the events of the Walpurgis Night.
Student Hiroko Takashiro and her friends Rie and Saki start their own unofficial witchcraft club at school. One day, Rie finds a mysterious book, and the group uses the perverted spells contained inside to influence the sexual desires of their classmates, including the student council president Nami Kozono, who has a crush on the young transfer student Reika Kitami.
After Kozono joins the club, they try to summon a demon in preparation of summoning the Devil himself on Walpurgis Night. The ritual backfires, causing Takashiro to have a change of heart about using magic. Kozono defies her and assumes leadership of the club. Vengeful, power hungry and angered about Kitami repeatedly rejecting her advances, she stops at nothing to achieve her goals.