Kousei Arima is a prodigious pianist who earned the nickname "Human Metronome" because his playing is flawless and utterly precise. With a stern mother and relentless practice, he won every contest he entered, winning the respect of fellow musicians and the applause of audiences. When his mother died abruptly, the shock left him unable to hear piano tones; he abandoned the stage forever. He keeps his piano locked in the attic, a silent reminder of what he lost.
Today Kousei is a quiet junior‑high student who hangs out with Tsubaki Sawabe and Ryouta Watari. Though he still clings to music, the grief over his mother keeps him from fully moving on. His monochrome existence is shattered when he meets the quirky violinist Kaori Miyazono, who pulls him back into the spotlight as her accompanist. A small deception brings the two close; Kaori"s vibrant energy slowly paints color into Kousei"s world. The encounter with Kaori awakens a spark he thought had faded, inspiring him to play again.