Every year, Suminoe-chou holds its ningyo matsuri on the Pacific coast, and Takumi helps run his family's café alongside childhood friend Mizuka and his mother Isana. On festival night he follows a beautiful voice to the water's edge, startles the girl singing there, and pulls her from the sea. With no safe place for the mysterious Shione to go, she ends up staying at his home—and before long, another girl named Matsuri transfers into his school, and the quiet rhythm of his days begins to change.