Kang Pi-o is known around school as an unrivaled talent — until he meets the mysterious Choi Jeong-yo and realizes he may have finally met his match.

With Jeong-yo now his classmate, a bitter Pi-o keeps his distance. But when the two are tasked with a joint performance, Pi-o finds himself warming up.

When crisis strikes right before the joint stage, Pi-o improvises a fix — only to wonder if it was a mistake when Jeong-yo's skills outshine his own.

With Pi-o determined to reclaim his love for music, Jeong-yo shows Pi-o how to have fun on the piano. Jeong-yo's family troubles catch up to him.

Intent on proving himself, Pi-o joins the Prague Harmonie International Competition and asks Jeong-yo to join too. Pi-o's obsessive practice takes a toll.

Years later, Pi-o is successful and world-renowned — but miserable. Hong Jae-in tries to let Pi-o know how she feels. Pi-o hunts down news of Jeong-yo.

Pi-o finds himself stuck deep in a slump, but can't seem to overcome his fears alone. Later, a familiar face suggests collaborating on a performance.

Pi-o faces increasing pressure to do the joint performance, but his issues with the piano only get worse. Jeong-yo finally steps in to help.

Pi-o learns the shocking truth behind Jeong-yo's kidnapping. Jeong-yo asks for Pi-o's help with a piano piece, but his harsh words leave Pi-o rattled.

Pi-o realizes Jeong-yo has been hiding a huge secret. With everything revealed, Jeong-yo turns even more cruel, and Pi-o falls deeper into despair.

As the Korean Symphony’s 80th anniversary concert begins, Jeong-yo and Pi-o face a turning point — but when the performance ends, only one person remains on stage.

After painful losses, Pi-o considers leaving music behind, but Jeong-yo shares his final feelings as their last four-hands performance begins.