魔法少女ピュア・セインツ～負けちゃうたびに、どんどんエッチな正義のヒロインになっていっちゃうの～

A certain city in Japan.
Since the appearance of the villian Mask de Roman, some people are able to affect others with the power of their erotic delusions.

Naito, a student, enjoys his daily life with this power, secretly hoping that one day, he'll be able to transform his whole school into a lewd place.

One day he witnesses a battle between Mask de Roman and the Pure Saints, a group of magical girls, in which the villian is killed.