Kiyoko Tachibana, a student at an integrated middle and high school for girls in Tokyo, met Akari Okusawa, who was wearing a bright blue dress, at the start of the new school year in her first year of high school. In contrast to the other students, Akari freely interacts with everyone and quickly becomes popular, and Kiyoko is attracted to her. Kiyoko's newly awakened feelings for her soon involve the whole class, and the situation develops into a disturbance.