Shunsuke is a pessimistic young man who was orphaned as a child. One day, drawn to a mysterious song coming from the next-door apartment unit, he meets Setsu, an old woman who claims she has been waiting for 400 years to become his wife. Assuming she’s demented, he searches her background in hopes of finding someone to take custody of her. In the process, he comes to embrace her as the mother figure he had been longing & agrees to marry her. But when his workplace learns that the woman allegedly owns a large estate and suspects him of swindling her, Shunsuke sets out to learn the truth about her past and uncovers a bittersweet history of love and loss -- and a map to the treasure long sought after.