"Let’s be a light like Eun, Ha, and Soo in a dark society!" Eun Soo and Eun Ha, a couple, run out from a successful music production company to show off their individuality and form the EunHaSoo band with Dong Eun. Meanwhile, Dong Eun, who was investing coins to earn living expenses, touches the band's money and loses it in an instant. Angry, Eun Soo and Eun Ha sell Dong Eun's guitar at a used market, and at that moment, Dong Eun appears with the money. As Eun Ha and Eun Soo encounter the lives of people who have purchased guitars in search of a guitar that means a lot to them, they realize what it means to put their heart into music. What does the guitar mean to Dong Eun, and what journey will the three go on to find it?