Based on the Internet novel of the same and written by Yeo-ni Gui, “Do Re Mi Fa So La Ti Do” is a touching love story with bittersweet elements. Jung-won wears a funny dragon suit, while working at the amusement park, and pours soda on Eun-kyoo, because of his taunts.
A short while later, Jung-won finds out that Eun-kyoo has moved into the house next to hers. Eun-kyoo now threatens to tell Jung-won’s parents that she works part time at the amusement park. To keep Eun-kyoo quiet, Jung-won agrees to carry his guitar for a week. Jung-won then starts developings feelings for Eun-kyoo, who is the lead singer in a band called Do Re Mi Fa So La Ti Do. Eun-kyoo also starts to develop similar feelings for Jung-won. The two soon become a couple.
With an odd twist of fate, Jung-won goes to the bands rehearsal room and meets a familiar person from her past, a boy named Hui-won. Their relationship makes everything make more complicated. 10 years ago, Jung-won and Hui-won were close friends, but because of a personal matter stopped talking to each other completely. Jung-won is now surprised to learn that her ex-close friend is now best friends with her boyfriend. Will their relationships survive?