Katagiri Natsuomi, a high school student living alone for two years, has a beautiful black-haired, blue-eyed girl move into the next room. The girl, Yui, is actual nobility, and her nickname is “Cool-de-rella” because of her indifferent attitude at school. When Natsuomi finds out that Yui doesn’t want to rely on others, but is actually quite naive, he decides to help her out. This is the beginning of a sweet and tantalizing relationship between two neighbors.