The port town of Nagisa has a nostalgic ambience. It is the only place where the star Nagi can be seen. The townspeople hold the “Starry Sky Festival” every December to worship their guardian star. However, it doesn’t concern Kei, who moved to the town with his sickly imouto Soraha. It was more important to him to get used to his new life.

At first, they faced a series of troubles, but Soraha’s health gradually got better thanks to the clean air in the town. He was able to make friends at his new school and adjusted to living in a rural town with few inconveniences, even without their parents around. However, there was one odd rule that he had to abide by: he must not let the existence of Nagi be known to outsiders.

One day, he has a mysterious encounter with a girl who had the same name as the star, Nagi. This is a love story between humans and the stars.