Machikado Mazoku follows Yuuko Yoshida, an ordinary high school girl whose life is turned upside down after a strange dream about a mysterious ancestor leaves her with demonic horns and a tail. When her mother finally reveals the family’s history, Yuuko learns that her household descends from the Dark Clan, a once-powerful line that was defeated and reduced to poverty by their mortal enemies, the magical girls of the Light Clan. By tradition and curse, Yuuko is expected to defeat a magical girl and offer her blood to the Demon God statue in hopes of restoring the clan’s honor and survival.
That impossible task takes an even stranger turn when Yuuko is saved from being run over by a truck by Momo Chiyoda, a magical girl who also happens to be her classmate at Sakuragaoka High. Momo is far stronger than Yuuko in both strength and endurance, yet instead of destroying her, she takes pity on her and starts helping her train while Yuuko struggles to awaken her dormant powers. As the two fall into an absurd routine of supernatural battles and school comedy, Yuuko is pulled into a growing rivalry with her generous frenemy, all while trying to save her family from the grip of poverty.