Miku Hatsune, Luka Megurine, and Zimi Samune have always been best friends. Bathed in an orange sunset, the three girls seal their friendship with a star-shaped charm they share, promising to stay together forever. However, a tragedy soon befalls the group and tears their bond to shreds. As the world around her turns a dull monochrome, Zimi can only watch as time passes—and her friends grow further and further apart.