Despite continuing to play in his unsuccessful band, Kohei is surrounded by good friends and a precious girlfriend and so he enjoys a normal life. But "one day" he loses everything. And although he knows he can never get his old life back, he decides to move on by writing a song.

As the last summer vacation of high school approaches before university entrance exams, Shun meets a shrine maiden named Nagi at a mountain lodge he visited with his friend Tatsuya.