Kim Seomin might look like a small, petite girl. At school, she's popular for her soft and babylike voice, cute looks and a surpringly small body. Teachers, students, and staffs -- they all adore her. The story differs, however, when she's not at school. Despite her deceiving, cute looks, she goes around the dark streets of Seoul, threatening people's lives like it's her favorite hobby. At night, her eyes turn red, crimson veins manifest through her immensely pale skin, and her artificial puppy eyes turn into violent swords, yearning for the blood of her criminals. She becomes a witch, a puppy to a complete .

She plans to keep her true identity a secret for her whole, entire life, especially to her school mates. But things don't go as expected when she accidentally bumps into Park Jimin, the hottest Kingka at school, in her witch self. Things are even harder for Seomin when she, including every single being in Seoul Private School, knows that Jimin has the biggest crush on her.