A girl named Mitsuki Kanzaki lives with her step-brother Yuya after her mother remarries. One day, Mitsuki is possessed by the self-proclaimed spirit of a young girl, Hiyori Kotobuki. Hiyori (in Mitsuki's body) must fall in love with Yuya to move toward the "Gates of Heaven."
K?sei Arima was a piano prodigy until his mother died when he was eleven years old. The shock of losing her made him lose any interest in piano, and his life has felt monotonous ever since. Then, when he's fourteen, his childhood friend Tsubaki introduces him to her classmate Kaori, a free-spirited violinist. Her enthusiasm reignites his interest in music and in life.