Han Tae Yi lost his will to live after the death of his older brother, who was a genius jazz pianist. To Tae Yi, transfer student Yoon Se Heon is truly an uninvited guest. Se Heon has been playing jazz that reminds Tae Yi of his brother since the first day he transferred to school and gets on Tae Yi's nerves. Se Heon also suspects that Tae Yi has a suspicious relationship with his friend Seo Do Yoon. Se Heon, who longs to play jazz freely and escape the eyes of his strict classical music professor father and Tae Yi, who wants to give up everything, was assigned to the same group for joint performance evaluation. As they practice together, they find themselves developing complex emotions for one another. However, just as their relationship begins to deepen, Song Joo Ha, a senior student who was suspended from school, returns to school, and his presence begins to stir up things between Tae Yi and Se Heon.