Gu Yeonseo is the marketing ace at AZ Company. Behind his perfect looks and abilities lies a secret: he is a Gumiho (nine-tailed fox) who managed to grow nine tails in just 200 years. Everyone believed he would become a Cheonho (celestial fox), but he chose a different path, going through exams and job searches to live life as an ordinary human. However, the identity he had meticulously kept hidden is compromised in a single moment: a mistake leads him to be discovered by the developer Yoo Minhyuk. To make matters worse, his magic doesn't work on Minhyuk! Determined to protect his peaceful human life, the Gumiho launches a mission to win over Minhyuk and his younger brother. A clumsy, yet close-knit, neighbors' romance from the Gumiho!