Suho and Hyeonseo, who once dated for six years, meet again as a youthful rich CEO and a piano instructor who gave up on her dreams. Despite the awkward reunion, the two start piano lessons for their respective purposes. Meanwhile, talented musician, K, accepts Suho's offer to work on a collaborative project and invites Hyeonseo as a fellow collaborator. Annoyed with this new partnership, Suho proposes that they stay and work at his house, which causes subtle tension between the three. Suho becomes confused after learning why Hyeonseo left him. Hyeonseo worries about Suho's health, while K doesn't hide his feelings for Hyeonseo. Suho and Hyeonseo embark on a bumpy romantic journey full of twists and turns. Will history repeat itself?