This is a story of a young woman and her coming of age in Japan. In the winter before her college graduation, Michiru receives a letter from a girl. Apparently, they are sisters who share the same father. Michiru has never met her father. Even though she had never cared about him, the fact the he exists begins to pique her interest. As she investigates him, she experiences many emotions. The youth of a girl is 'like the music pouring out from the world,' and fragile like a raindrop.