While on the run from an evil Atsunmo, the divine entity Myu desperately searches for someone worthy enough to become a magical girl and defeat the horrible monster. Just as the demon catches up to Myu, he spots a high school student who looks like the perfect candidate. Pretty hair, a kind face—she has it all. But to his surprise, seconds after Myu gives this student the abilities of a magical girl, she pulls a cigarette out of her pocket.

The girl, named Kayo Majiba, is actually an aggressive delinquent with an attitude that betrays her appearance. She has no problem taking out the Atsunmo, defeating it in just a single punch. However, Myu is now faced with a greater threat: Kayo herself. Nonetheless, it is Myu's duty to guide Kayo toward the path of defeating evil. But can he carry out his responsibility when there seems to be more to Kayo's tough demeanor than what meets the eye?