Masaharu spends noisy days together with his imouto who’s a little lacking in morals. On his way home from school one day, he came upon a mahou shoujo surrounded by people in black tights who could easily be mistaken for perverts. He recognized her as his osananajimi who had left a year ago. The next day, the bad guys turned to attack him and other mahou shoujos showed up to fight them. Will they be able to protect him?