Lim Hyeonseon has followed the well-traveled path of life: he graduated, secured a job, and got married. But the marriage ended in a divorce, and on his 40th birthday, he finds himself lonely and constantly bombarded with questions about his non-existent love prospects. In search of anything resembling fulfillment, Hyeonseon recalls an old electric guitar he bought 16 years ago but never attempted to learn. He hesitantly enrolls in a music class taught by the spirited 24-year-old Cha Yeoreum. Although Hyeonseon is persistently self-conscious about his age, seeing people of all ages so excited to learn fills him with newfound enthusiasm. Most unexpectedly, he befriends his young instructor and soon realizes just how much he enjoys Yeoreum's company and boundless energy. But Yeoreum's feelings seem to gravitate toward love, and no matter how much Hyeonseon tries to draw a line between them, it appears impossible to resist the pull of a summer romance. [Written by MAL Rewrite]