Haruhiko Amami's home town, Narasakicho,
Riko Fukumine was just a young girl when she lost her parents. The Amami family adopted her and she and Haruhiko became non-related siblings. Though neither admitted to it, they had fallen in love with each other. But due to financial difficulties, Riko had to move away leaving Haruhiko broken hearted.
Years later, Haruhiko is a teenager attending high school. Kirino Konosaka, a junior to Haruhiko in the same school, come to wake him up every morning and even prepares breakfast. In truth, she has a crush on him but Haruhiko is clueless to the fact. However, Kirino was satisfied with their relationship because she and Haruhiko spent their mornings together everyday.
On their way home one day, they suddenly saw Riko waiting for them at Haruhiko's home. After so many years of separation, Riko has finally returned to live with Haruhiko and his family again. And it seems Riko and Haruhiko's feeling for each other never faded during their time apart. Kirino steps down for Riko and stops coming to Haruhiko's house in the mornings, but her feelings for Haruhiko are not as easily put away. There's also the eternal rainbow and the 'Gift' power, a mystery that may be tied to Riko.