In the late 1960s, C’est Si Bon is the go-to music venue where every acoustic band aspires to perform. It is here that Geun-tae, an innocent young man from the countryside, encounters the talented young musicians Hyung-joo and Chang-sik. Together, they create a band named after the venue—the C’est Si Bon Trio. As the trio navigates their musical journey, they are joined by the enchanting socialite Ja-young, who becomes their inspiration, leading to the creation of heartfelt love songs. Geun-tae’s sincerity captures Ja-young’s heart, but their paths diverge when she seizes a rare chance to pursue an acting career. Two decades later, the hidden tale of their romance, music, and youthful days at C’est Si Bon is finally unveiled.