Kidou Eita is a first-year high school student, excelling academically and expressing contempt for romantic relations. He lives a normal school life along with Harusaki Chiwa, his childhood friend whom he regards as a younger sister.
One day, the school’s prettiest girl, Natsukawa Masuzu, suddenly declares her love to him. However, her real purpose is to establish a fake relationship, deterring those around her from asking her out. To this end, she makes Eita her boyfriend over his objections.