By day, Eun-gyeol, a young CODA(Children of Deaf Adults) boy, is an acclaimed model student consistently claiming the top spot at school with his impeccable personality. However, by night, he lives a secret life as a band guitarist, unbeknownst to his parents. On a night illuminated by two moons, Eun-gyeol stumbles into a peculiar music store, propelling him back to 1995, where he encounters his father during high school. Yet, he soon discovers that his father's first love wasn't his mother! Enter Se-kyung, the first love of all, who had left for overseas studies. Her abrupt return to Korea sparks a series of events, prompting Yi-chan to form a band in a bid to win Se-kyung's heart. Eun-gyeol joins Yi-chan on this journey, driven by a desire to protect his parents.