Ichika is a high school musician who can enter a mysterious place called “SEKAI,” where she and her friends express their innermost emotions through music alongside Hatsune Miku. One day after giving a live performance, Ichika meets a new Miku that she has never seen before. No matter how hard this new Miku tries to sing, she struggles connecting with the hearts of her listeners. Miku must rely on the help of others to find a way to sing again.