Amidst all of the issues that any teenager girl usually has, Aika Tsunaboshi also secretly an Magical Girl. Much likes the ones you would typically see in anime and manga. Except these ones also hunts demons on the side.

One day, while fighting against her nemesis, she is forced to make a decision and temporarily transfer her powers to someone in her family. Which according to her partner (AKA Sacred Beast) Nyamo, the Nekomata, was intended to go to her older brother, Akira Tsunaboshi. Who is always mistaken for a girl and barely able to form a full sentence towards strangers, which leaves him prone to many misunderstandings.

Akira is already in his third year and everyone in the school still recognizes him as one of the most popular "girls" on the school. Making him quite unapproachable for most students, who thinks Akira lives in a higher place than the rest, rendering him to be quite a loner.

However, during the transferring process, Aika got cold feet at the last second and her partner, alongside her magical powers were sent somewhere else. About to be stricken down by her assailant, Aika is saved by a strange fat man. Her savior... just happened to be one of her teachers, Shinjirou Tsunaboshi... and her uncle, who just happened to be passed out drunk in the gym storage nearby. Which she so utterly despises due to his being drunk more often than not, near perpetual state of hangover, his carefree nature, unrensponsible and perverted tendencies that earned him the title "Ero-Sensei" which caused many antics and headaches for Aika to deal with most of her life. The shock of seeing her uncle wearing her uniform, a frilly dress, alongside a set of cat ears, tail and everything made her pass out on the spot.

By the time Aika woke up, not only he was casually partying with both her partner Nekomata and the demon, became best friends with them, as well but also convinced the two to form a strange alliance between himself, her demonic nemesis and through Nyamo, sent his unprecedented proposal to Arcadia, the group behind managing and recruiting all Magical Girls.

Would Arcadia even consider Shinji's suggestion and his abnormal circumstance? Will Aika be able to handle yet another stress placed on top of her social life? Will Aika's powers ever return to her? Even if it does, will she be able to manage to put up with her troublesome uncle for the sake of justice until then? Only one way to find out!