In the heart of a prestigious art academy, the paths of Kang Bi-o and Choi Jeong-yo cross, two young piano talents who could not be more different. They both carry their own 'sonata'—their own life story full of personal struggles, dreams, and hidden scars. From their first meeting in the classroom, a charged tension hangs between the two; they are each other's greatest rivals, yet simultaneously feel an undeniable, magnetic attraction due to their shared passion for the piano. When their teachers force them to play together—a 'four-hands' technique in which four hands must share one piano—their rivalry slowly transforms into something deeper.