Piano prodigy Kosei Arima dominated the competition and has become famous among child musicians. After his mother, who was also his instructor, died, he had a mental breakdown while performing at a piano recital at the age of twelve. As a result, he is no longer able to hear the sound of his piano even though his hearing is perfectly fine. Two years later, Kosei hasn't touched the piano and views the world in monochrome, without any flair or color. He has resigned himself to living out his life with his good friends, Tsubaki and Watari, until, one day, a girl changes everything. Kaori Miyazono, a fourteen-year old audacious, free-spirited violinist whose playing style reflects her manic personality, helps Kosei return to the music world and shows that it should be free and mold breaking unlike the structured and rigid style Kosei was used to.