Touka Minamori is a lonely college student with a secret lewd side whose life is upended when her childhood friend, Kokoha, recruits her to become a magical girl. To fight monsters known as "libidos," Touka must transform into Crystear, a process that requires generating mana through extreme public humiliation and sexual arousal. After a scandalous debut in her college classroom and a suggestive first battle, Touka is thrust into a world where her own modesty is the key to her magical power.
Touka discovers that her magical power is fueled by embarrassment and public shaming. To defeat the "libidos" terrorizing the town, she is forced into increasingly provocative situations, eventually discovering that her own hidden perversion generates immense mana. While she successfully defeats several enemies, her growing reputation as a "lewd heroine" attracts libidos from across the country, promising more chaotic battles to come.