Yui Kayama is a beautiful high school girl with ringlet blond hair. She is extremely sensitive to stress and easily gets an upset stomach. Because of this, she was given the nickname "Miss Bowel". Her mother is Aoi Umidori, a former actress. Her father's company went bankrupt, and her mother and father are divorced, and her father is currently on the run overseas. Her grades are not bad, but she lacks common sense due to her raised as a young lady in a box.