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.

Naito is agonizing about the loss of his hero, when a girl appears in front of him and tells him, he has been chosen as the next Mask de Roman.

Now Naito has to fight against the Pure Saints while aiming for his dreams.